21K -> 28K too much...

[Deleted User]

I have been running for 7 months and successfully completed a HM in April. I run about 40K monthly for past 2-3 months. A few weeks ago I was out running with a friend and planned to do 25K but ended up doing 28K (again, the farthest till then was HM). While running it was fine but then, and increasingly the day after, I was stiff and paining and in places where it had never hurt before.... It has been 3 weeks now and I am still not back to running (apart from a 6K test, which was OK).

Obviously I have over extended myself, and that was not smart. 28K from 21K is about 30% more, not good.

I have a few questions in this regard:

1. What may be the source of these aces and pains? (I don't expect a medical diagnosis just from your experiance). It was sore also in places never before hurting such as the foot and the heel (acheles tendon I think). I mean, is it likely just over-extending myself or possible damage?
2. Should I get an XRay of the foot to rule out minute fractures?
3. When I feel right should I just resume my normal runs (no less than 10K) or should I take it was down first?

I was planning on a full marathon in October but now think it wiser to wait till March and use the time to build myself better. Apart from loggoing miles, can you suggest various routines for strengthening legs/knees as well as stretching?

Thanks!