I had a c - section six months ago i feel lower abdominal cramps like period pains went for scan they say uterus is enlarged.what could be the cause ?

See your doctor: Symptoms and concerns like these mandate a thorough evaluation by your doctor. Only after such an evaluation, which may include labs and radiographic examinations, can he/she let you know what's going on and how best to help you.

Be seen: You could have several things, be seen for an exam and diagnosis. It could be be a hematoma, infection, or other things.

Needs further eval: An enlarged uterus can be due to multiple things such as uterine fibroids and adenomyosis. You need to be seen by an ob/gyn, preferably the one that did your cesarean.