Help!

So me and my boyfriend have been together a little over a year, I really love him and he's always so amazing to me.

Our relationship is healthy besides the fact he won't stop bugging me about finishing inside me..

I started birth control a while ago and I let him do it last month, it's exciting but it seriously freaks me out afterwards, I don't want to be pregnant.

For the past three days, during sex he constantly dirty talks about it and constantly asks if he can, even after I tell him no. Yesterday and the day before yesterday I let him but tonight he just wouldn't stop. He listened and didn't do it and I tried to explain why it freaked me out. All he said was he didn't understand and I can't get pregnant on birth control so he doesn't see the big deal.

I don't know what to do? Am I overreacting?