Suddenly not liking it?

So over the past year I have lost interest in having sex with my husband. Its not that I don't find him attractive because I do. I get in the mood everyday but when it comes to actually doing it my body freezes and no longer want to. Like we get to foreplay which is amazing but it's the actual act of sex that turns me off? If I just push past the feeling and we do the deed it feels great. I'm not sure what's going on.