Tmi Help!!!

My boyfriend and I have had sex and it's great but some times when he goes deep it hurts but not all the time. why does it hurt? is he hitting my cervix or something. We try different positions some are better but it still hurts. And every time we have sex we use a condom. The some brand and Same kind we have been using for a year. Has this happens to any of y'all? How do you fix it? Do y'all know what is causing this? Thank you!