3 months postpartum pain

As mentioned, I'm suffering chronic pain at 3 months postpartum with my second baby. I have had this pain almost every day for the past couple weeks in my abdominal area, very crampy/squeezing for long periods of time. While it's not excruciating, it's constant enough to make me want to curl up in bed. It is accompanied by nausea and frequent bowel movements. I have also gained about 7 pounds. I'm 3 weeks into being on the mini pill after not being on birth control for about 10 years and have had 2 periods in less than a month. Does anyone know what is happening? I can't afford another hospital bill and my OB keeps giving the "it's normal" answer. I haven't been wearing my belly band and I'm hoping i didn't mess up my muscles.