I had a great deal of pain after my second c-section and it was only when I asked the dr. to renew my pain meds that she said, wait a minute... you shouldn't be in this much pain for this long. I agreed completely! ;} She asked me to come in and she found that I had endometriitis. I have no idea how to spell it, but you get it, right? The key is the -itis part. Not -osis. It's a swelling of the lining of the uterus, if I remember correctly. It needed to be taken care of with antibiotics. Good news is, as soon as I started taking the meds, I felt much better... completely better within a couple of days.
I don't know if that's what you have, but I would certainly ask your dr. In my case, it wouldn't have gone away by itself and would have gotten worse without treatment. On the other hand, it wasn't serious, and went away quickly. Good luck, and congratulations on your new baby! ;)