Sex hurting while pregnant, then stopping

When I was about 6 weeks pregnant and I would have sex, it hurt really bad. It hurt when he went deep and I felt tighter than usual which caused a lot of pressure on my stomach I felt like. Now I'm about 8 weeks and we had sex last night and it didn't hurt at all. No tightness, and when he went deep it didn't hurt at all. I'm worried that something is wrong with the baby or I've had a miscarriage. On top of this, my stomach used to poke out a little, now it's almost flat. It's still hard but there's not a bump anymore. My drs appt isn't until Wednesday and I've been going crazy about this for about a week now. Does anyone know what's going on??