Can’t stick it in

Both me and my boyfriend are virgins. We’ve tried MANY times to have sex and every time the pain will be so bad he can only stick the tip in.

I’ve had sexual assault trauma in the past, and i’m wondering if that could be the reason for the pain? Or is the pain something I should go see the doctor about? Or is the pain normal?

Either way, he’s lovely about it and will stop every time I say it hurts. He’s not pressuring me at all, but I really want to do this. Mentally I feel ready. Why won’t it work? Any tips?

I also don’t know if this is related, but I can not stick a tampon in at all.