Painful sex 😔😣😞

So my son is 8 weeks today. My fiancé and I had sex last night. Remind you this is not the first time. We had sex before around 5 weeks and 6 weeks. Every time he pushes deep inside me it hurts. I had my 6 week appointment and I told my ob what happens. She said everything looks fine. I love sex but this sucks. We went almost 3 weeks without having sex because he was sick. We did it last night and it still hurt. Anyone else noticed a difference. This is my 4th son. my last two sons with my ex husband sex was fine. Maybe it's because my fiancé is heavily blessed in that department. I don't know. I hope it gets better. I don't like this.