first time pain (sex)

so my boyfriend and I decided to have sex. I've always been pretty scared to because of misinformation and such but I love my boyfriend and trust him completely so I was wanting to give my first to him. he's very reassuring and throughout the act, kept asking me if it felt good/hurt. he also told me that we could stop at anytime I wanted. he was really gentle and slow but it hurt like a motherfucker when he went in, which according to him, he did not even manage to put the whole tip in completely before I would cry in pain and he would pull out. I was thinking I might have been too scared/nervous and that caused me to be tense which caused pain. any tips on how to make the experience better?