New relationship sex

I'm so insanely in love with my boyfriend and we almost had sex tonight for the first time with each other but we didn't have condoms that fit him and my roommate was home so it was bad timing. I literally trust this boy with everything and definitely see a future with him but I am so nervous to have sex with him. I believe I'm pretty small because my last boyfriend was kinda small lol but my new boyfriend is pretty big and I just don't wanna seem like I don't know what I'm doing or anything idk. I just need some tips on being more calm and letting it happen I guess idk I'm just nervous but I want to do it so bad. Thanks everyone :)