sex after my first baby

so me and my bf have been having sex after our first child and I have not been to my 6 wk checkup yet to get cleared by my doc and get my new birth control. The thing is we have been having unprotected sex for like 2 wks now and he cums in me every time. I really dont wanna get pregnant again especially not five weeks after our first son was born. We are both on the same page about this but every time he still finishes inside me. Its nerve racking.