Cramping after Pooping

I’m 10 weeks postpartum. Currently going to pelvic floor physical therapy due to muscle tightness and scar tissue on 2nd degree tear.

I’ve been spotting the past couple days along with cramps. (OB thinks my body is trying to start its period, or I’m just having breakthrough bleeding).

Today I picked up my 13lb baby in her car seat carrier. After I did that, I had to go to the bathroom. I had a BM and now I am cramping and having lower back pain as well, like a mild/bad period.

Could this be from picking up her car seat??

I am also BF 3-4 times a day (no pumping).