Sex, help?

I’ve only had sex 4 times with my sexual partner it is still rather painful although each time he is able to go in further until the pain is too much for me. he said he is able to put about 3/4 of the way in now. When we have sex I find that when he goes in further I get a cramping feeling, kind of like period cramps. Is this normal? And is it normal for it to become less painful each time? We have done it once a month.