confused body need help ):

Amanda

a few months ago my bf and i tried anal and i loved it!!!! we've been doing it since and it's been amazing but the last 2 times we've tried my Body is just like nope and when he finally does get it in it hurts SOOO bad to the point where we have to stop for a while and then not do anal I need help bc he likes a it and so do i, there's plenty of lube and I'm super horny so idk what's wrong please please help ):