Period after having a baby

Before I got pregnant with my baby girl who was born in April I had very regular periods with not many PMS symptoms, some cramping but totally tolerable. I'm on my 3rd cycle after having my baby, first cycle exactly 8 weeks post partum, 2nd cycle 28 days after. This cycle was 5 days late. Also, when my period starts I feel like my vagina is going to fall out, it just hurts like a deep muscle hurt with or without tampons. I never had that feeling before having my baby. Anyone else experience this? I have formula fed from the start