My boyfriend doesn't fit and I'm so sick of it.

So I've had sex a few times before but never had a boyfriend and I'm finally in a really happy relationship. We're going really well but we've tried to have sex so many times and I literally think he's just too big for me. I thought my vagina was pretty loose but I can't even get him fully in with out screaming in pain!! Someone please help with any suggestions! I just want to be able to please him and myself! X