My fiance is freaking out of how it feels downtown

So lately my fiance been overwhelmed that he's not lasting as long as he used to. We would have at least 3 rounds or more. And now its 1 round and come back later (which I'm not the one complaining). We are still trying for a baby. My curiosity is him saying that it feels like he's being pulled in during sexy time. He mentioned that it usually feels like I'm pushing him out.( this isn't the first time I've heard a partner tell me that). I think its normal i think some men forget that the cervix heightens itself to go deeper.