Sex in general

Well me and my boyfriend haven't had sex in two weeks and some days since our jobs require us to be part for long periods of time well Dec 27 we tried having sex and of course it hurts when he puts it's in which I felt this before since it's been a while and normally it eases but this time it didn't I hurt none stop this was the day before I found I was pregnant. Can anyone tell me the reasoning behind it. Please