I can’t lose my virginity

I’m 18 and my and my bf have been dating for a year now and we feel ready and we’ve just started trying to have sex. I’ve tried at least 5 times each a different occasion and I can’t seem to do it. We’ve tried different positions and used lube and it still hurts unbearably to have sex I can’t even get him through. I can only fit like one or two fingers in and I try to relax and stuff and I feel like I am most of the time but I still can’t do it it just hurts too much. What should I do I haven’t seen a gynecologist yet but I’m more than interested in getting a professional opinion but could it just be my fault please give me advice