Why can't I feel when I orgasm

Ok so like it says in the title I can't really feel when I orgasm. But it's only during sex. if I masturbate I can feel it just fine although it's not a big immense feeling that everyone says it is. But during sex I can't tell but I know it happened because I check after wards and it's obvious I had an orgasm. I have no idea why this happens and I tried looking it up and no one really had an answer for it. can someone please help me?