Please help

I have been in a relationship with the same guy for two years, but something unexpected happened last week and I would like to know all of your opinions.

A little back story - I am 15 and he is 17, we’ve known each other since we were little, and our parents are very good friends. We became way closer our 7th/8th grade year and decided to start dating. So we’ve been dating for two years🤩

Since we are neighbors, I go to his house a lot, just to hang out, we’ve never done anything. Just last week, we decided we were both ready to give it a try. He had a condom and I’m already on birth control, just before you say anything 😂 it hurt pretty bad(it was big)so we stopped and decided that we would try again tomorrow. So I need help ASAP!! How can I loosen myself up a bit so it’s more enjoyable and less painful?

XOX, thank you