Sex after baby causing cramping?

I hope this is in the right group, I didn’t know where else to put it!

I had a baby June 26th and me and husband have only had sex three times postpartum. The first time was miserable and the second felt a lot better. So last night we go to have shower sex and it’s great and I’m on my period (unfortunately) and tonight I am cramping SO bad like I could cry bad. Is this normal? Should I call my OB???