You need to go to the doctor to rule out lots of things - none of which are very likely but all of which should be checked for. Iron is just one example. It's not a waste of the doctors time, if the doctor were to suggest that you were go see a different doctor.
When it comes to diet I guess that you're probably living at home and more or less subject to what the family eats but do your best to avoid anything processed and if most of what you eat is plants or animals you'll be doing well.
If it is over training but you're already over the 'loss of motivation' stage then you're probably beginning to come out the other side. You need to do easy running only for a few months slowly building up the volume. You should be feeling good after runs. No pain, no gain is totally inappropriate here. After a few months do a parkrun and see how you get on. If you break your PB then you're probably ready to add a little intensity to your training, if you don't just keep going at the easy running.
Thinking of your training as a pyramid where the slowest running you do is at the bottom but is the biggest block and the fastest running you do is at the top and is the smallest block. If you don't do enough of the easy running then your pyramid gets top heavy and collapses otherwise known as injury or over training.
BTW, I'll bet you anything that you could get a huge PB just by doing easy running.
P.S. In case I wasn't clear - Run slowly! Only run slowly!
Al_P - Orthotics got me running when I couldn't run for more than a few miles without terrible shin splints. In the end they caused a lot of trouble and probably played a part in the injury I'm coming back from at the moment. I've ditched them and so far so good. It does appear to have changed my gait in a positive way in some respects although competent physio could possible have done the same thing. If you do go for it, please, please, please get them cast by a podiatrist/orthotist. In my experience physios tend to think that they have expertise in this area which they simply haven't got.
ST - Sounds like you properly hurt yourself. Go see a professional.
CW - Hope you get over the niggles soon.
Pi Man - Nice improvements - well done
OT - I'm with TT - I think of easy running as around about 70%, if you do it at that level you should be able to do a bit more - slowly you'll become a better runner. That said, if you're following a plan, it's always good to see a plan through rather than chopping and changing too much as you go along. As an aside I would expect ironman training to have a bang for your buck approach to running training especially as you'll get a lot of work in on the bike at the lower heart rates. If you're doing ironman great, if you're just running maybe follow a running specific plan?
TT - Very nice!
Wardi - Nice (but expensive) 5k. Tempo and 10k pace work are what come to mind on how to improve 10k relative to 5k when endurance isn't an issue.
TR - A fast 10k and an 18 mile run. Sounds like there's a sub 2:50 genie in the back of your mind. I have huge respect for the time that you allow for your kids.
Lev - Hope you're off the bench soon. If you think about it, it makes sense that you get injured when in your best shape - a lot of injuries occur because we push the boat out too far.
DS2 - You really want to see a bit of progression in your training over the 16 weeks. If you keep running the same distance runs at the same pace you'll not get much fitter. Also I don't see the purpose behind any of the runs? You should be thinking of lactate threshold runs, marathon pace runs, medium long runs, easy runs, VO2 max runs etc.
Jonny - Congrats. That's a huge improvement.
Puddletown plod 20k for me today. It was actually a training run in a race but I wasn't sure how it would go as I did 68 mins yesterday and these are the only 2 days in my 14 day cycle that call for running on consecutive days. Ran it by HR which helpfully reined me in especially on the hills. Managed to dip in under 1:40 which is 11 minutes slower than 2 years ago but I enjoyed this race a lot more.
ok, so I got contradicted twice - which is fine as I was using the N=1 + memories of those around me when I was that age as a basis for my hunch. It didn't feel right though so I've had a trawl through the rankings on power of 10 - they only give the top 200 for the 3k at u-17 level but I've gone through about 25 - 30 entries without finding a single person who has failed to progress over the last two years. That doesn't definitively mean anything. Isaac could easily be the exception that proves the rule but still it is unusual and bears a little further examination.
I had a look at your power of 10 profile Isaac and the thing that jumps out immediately is the number of park runs that you've done. You did about 40 in 2011 and a dozen or so in 2012 when you had your loss of motivation. That's fine if you're taking some of them as easy runs but if you're going all out which judging by the times it looks like you were most of the time then you burn out and there's a decent chance that that is what has happened here.
You should go see your doctor, explain what has happened and ask for blood tests to rule out iron deficiency and anything else the doctor can think of. This is an area that you should be politely insistent on. If you have any underlying iron deficiency then it'll need to be treated appropriately (N.B. Do not ever self-medicate for this, too much iron is just as big if not a bigger problem than too little).
Assuming you get the all clear from your GP you need to back right off the intensity of your training.
Everything needs to be easy and you need to listen to what your body is telling you. If it says to take a day off, then take a day off. If it says take a week off then take a week off. As Blisters said you can do 10 years of steady improvement once you get yourself sorted.
Do runs that you enjoy - I personally get a kick out of running along a cliff path near where I grew up or in the New Forest where I come across wild horses and deer. Others love running beside a canal. Whatever you enjoy is what you should do.
Think about taking up another sport as well where the focus - at least initially - will be more on skill acquisition than cardiovascular fitness.
If it is overtraining then your youth may help you to recover more quickly relative to others but it won't seem that way to you. Some people take a few months, some a few years and some never recover. In many of those instances it's the attitude of the athlete that determines their speed and chance of success. Ironically it's the more dedicated ones that find it the hardest because the cure is the opposite of what they have been doing.
I would have thought that there was plenty of time to focus on 5k for the next 4 -5 months before moving on to ultra?
It's difficult to tell you exactly what you should be doing training wise without having a detailed knowledge of where you are now and how you got there but now would be the time to build mileage including at tempo and marathon pace as well as easy. The key to 5k is your VO2 max but that can be maxed out in 6 - 8 weeks (and you may not need to in order to go sub-17). You'll need to make sure that you have the raw speed but again that can be developed quite quickly. You'd probably target a small cluster of 3 - 4 races and bring all the training together just before and during that.