Here's my advice: Fake it.

Otherwise, if this guy is at all normal, he will start seeking someone who makes him feel desired.

You having orgasms isn't absolutely necessary to the two of you having a sex life that is mutually pleasurable. If physical closeness to him doesn't really interest you, then I would suggest you have no real future with this guy.

There's more to this story than you are disclosing here. That's your business. No one who previously had an interest in sex just suddenly loses it, with no clue as to why. Ask yourself what happened . . . and give yourself an honest answer.