Can't feel him inside of me?

Ok, TMI for some, I'm really sorry if this makes anyone feel uncomfortable.

So my husband and I have a good sex life, I'd like to think. We've been married only 4 months so we're still newlyweds, we have sex maybe 3-5 times a week. However recently that's been lowering, slightly. We're both stressed because I've moved from England to America so there's an entire immigration thing going on too. Sometimes when we have sex, it's great! It truly is. The last time we had sex about a week ago now I absolutely loved it and it turned me on so much, and I sure as hell felt him inside me. But today? Nothing was wrong, it started off and we were both feeling good. But the second he went inside of me? ... my heart sank because I knew it'd be another bad time again, because I literally did not feel him what so ever! And I just suddenly cut off emotionally with him, and he came within 5 minutes.

I'm just so confused as to how one day I feel him, and other days I don't feel him at all. Because obviously it's not the fact that he's too small, otherwise I wouldn't feel him in the first place.