I took up running a couple of years ago and have been a fairly consistant runner ever since. Up until last month i was running fairly regularly (3-5 times a week, short runs before work, longer runs at weekends) and following a marathon training plan. I had a minor operation and stopped running for two weeks on medical advice.  I started back quite carefully, going for gentle jogs and not worrying too much about timings. However, recently when i even attempt to run i get a terrible pain in my calfs. it gets so bad i have to stop and walk which aches too. what is more worrying is that it appears to be getting worse. this morning i couldn't even manage a mile before having to hobble back home. I haven't changed any of my usual warm-up practices or anything and am at a loss as to why this might be happening. I'm getting a little concerned.