pelvic pains

My DD is now 5 months old & 5 weeks after she was born i started bleeding again followed by cramping pains & lower back ache. Went to doctors who said i developed an infection which required antibiotics. There was the question of retained placenta but everything kind of settled down. Ever since i have been getting pains on & off sometimes quite painful & i have to breathe through it. Had an ultrasound a few days ago & they said everything looks normal except for a fair bit of fluid. I also have some small cysts on my ovaries but apparently they are nothing to worry about. I thought maybe my body is just trying to return to normal, i am breastfeeding so my AF hasn't returned yet.
Anyone else experienced anything like this??