Advice to make it not hurt?

I got out of a toxic relationship a couple months ago and now I am in a healthy one. It is true when people tell you "the healthy relationship after the toxic one is the hardest". With my ex it didn't hurt most of the time. And I was on depo. The last shot I got was june of this year. Im confuses on is it the birth control making it hurt when it goes in? Is it just that I'm not used to bigger guys? What can I do to enjoy and be interested in having sex more often because right now its been hurting so bad that I dont want to try again. But I want it to stop hurting so I can enjoy it. Advice? Please! (I turn 20 in september)