Help 😕

My boyfriend and I have been together for a while now. We have been having sex for awhile, but for some reason the last two weeks he just instantly cums. He literally just goes in me, and instantly cums. We both don’t know why, and I can tell he feels bad, because he knows I’m not satisfied. But I know it isn’t his fault. He’s just become to sensitive to do anything, and we don’t know why? Please help.