RRR - I echo all the sentiments made so far, you must take heed of the warning your body gives you. As I said on here, 2 weeks ago my long weekend run resulted in a sore and tight calf. I took a few days off and even though it was still slightly there when I resumed, it now seems to have vanished. Taking a few days off - as hard as it was to do - was without doubt the right decision and I doubt the time away will have a particularly detrimental effect on my time.
I also have experienced some of the same episodes of fatigue and some runs that just felt so tough to complete. It takes it's toll but I also think it's extra tough at this time of year as we're all (unless you are supplementing) in vit D deficit and in desperate need of some sun on our skins to boost our energy levels.
I seem to have come back to a good place with it now. The calf pain has gone but also my runners knee is barely noticeable, as if I have somehow gradually run it off. I haven't even been keeping up with the stretching, rolling and exercises, it's just healed itself (almost). I'm starting to feel fresher on the runs too so i've no doubt that everyone has these bad patched (and during a marathon itself) but that you can grit your teeth and things will turn around eventually.
Besides all of which, we really are getting toward the end now. Taper starts in less than 2 weeks so just 12 days or so of full training and then things will get easier anyway. Keep going!