"I take all the regular vitamins" wotsis mean, Miss Goodnight?
You shouldn't really be feeling wiped out by your period, so if I were you I'd deffo be down to the nurse at your surgery for a full health workup. At the very least I'd want to make sure there's nothing else really wrong that could be causing/contributing to the period weariness. As well as checking your bloods etc are ok, she can also check your records for any problems you've had in the past that might have some effect on how you're feeling now. If she/you have any further concerns she can get you checked out by the doc. It might just be what you're eating. In which case the nurse who gets to see you will be able to advise you on your diet and which nutritional suppliments would be most suitable for YOU (much of the "usual" range of vitamin tabs don't address period-related health)
As much as a webdoctor is helpful in providing information about disease and symptoms, if they can't see you in the flesh then they can't properly diagnose your symptoms.
Mine's 2.5 miles. I don't push it very hard either, but I do get a bit of a "glow" on. Mind you, half the heartrate increase is 'cause of the scares I get from car drivers (but that's a discussion for a different thread ;-)
Thing is, if it's enough to raise the heart rate and then you will feel a bit wobbly if you suddenly sit down and do nothing, so just keep wandering around the carpark/office a bit until you've cooled down. You might continue to feel a bit "sensitive" because of the increased alertness that comes with exercise, but it'll wear off in time.
Yeah, I found that too when I started biking to work after years of not. Only takes me 15mins, but it's enough to work a very mild sweat.
I'm fine now, body adjusted, but you do need to accept that your heart rate will be high when you get into work. And therefore, as you've learned, you're not only a bit more alert to everything going on around you, but sitting down immediately and trying to work quietly is just going to make you feel ill...
Firstly, stay on your feet and give yourself 5-10mins to unwind when you arrive (go get more water, walk around the office, open your mail while standing up, etc).
Secondly, and probably more importantly, you're just not eating enough! (Add juice and/or toast, and fruit to your porrige) and it would be wise to eat again when you arrive at your desk. Nothing big, just a piece of fruit or yoghurt or nuts. And another small snack again about 1.5hrs thereafter before lunch. See how it goes and adjust as necessary.