I completely understand. With my ex husband we were the exact same way. After about 3 years in I asked him why we didn't have sex anymore, like once a month if I was lucky. He just said he was too busy, or some other excuse. He watched a lot of porn and was no longer interested in me. We were together for 8 years and I never had an orgasm. I have been with my fair share of men and never had one till I met my fiance'. I don't have a reason for it, other than to say he is wonderful. I feel safe with him.
You need to talk to him about your feelings and see if he can understand where you are coming from.
I wish you the best of luck