Something's wrong with me

Two things wrong actually. First one, in the past when I've had sex my lover boy has gone in no problem. Now though it's hard to get it in. I get wet but he can't just slide in. It's like when he's about to I close up like I've been sewed shut. I might have added to much detail I apologize but it's true and I just need advice or a logical reason why. And second one, when it's forced in and we get going it starts to hurt like he's hitting something in my lower abdomen and I have to make him stop for a second till the pain stops.