Help!!!!!

So I just ended my period on Sunday and me and My Husband we’re trying to have sex yesterday and Monday and the pain just hurts so bad I don’t know why and I have never experienced this before I don’t know what it could be and I’m just torn because I hope it’s not something serious and I don’t want to ruin our relationship. It hurts when he goes more than halfway in and like I said I have never experienced something like this before so I have no clue what it could be