Please, don't marry him. Do you want to deal with these feelings of rejection for 50 more years? 95% of men would rather peform oral on a woman than eat.
Lol. While I enjoy giving oral, I'd think most men would prefer to eat for survival than eat out a woman. Frankly, I'd prefer to do both
To the OP, I am also engaged and the reason I am here is because I too have/had issues in my relationship that I want fixed prior to marriage. I suspect that at the very least your partner doesn't like to do oral. If so, that is a problem, hwoever if your fears are confirmed that your partner doesn't want to have sex with you much/at all are true then yes, you need to at least postpone the marriage.
It's one thing to go through life without something you enjoy, such as oral sex. That will be your call if you can live without it or if you need it. Sex itself though, I doubt anyone can really go the rest of their lives without having a partner that wants them and desires them, and I think this goes a bit moreso for women who are raised to expect men to come onto them.
When is your marriage scheduled to take place? Have you asked your spouse if he is interested in having sex with you anymore? If not, do so but do it in a non-accusatory way and whatever you do, do not freak out over his answer, even if he says that he's not that into you anymore. If you want him to be open and honest with you in the future you need to set up communication with him where he knows he can at least say whats on his mind without getting an earful.
What you do with that information afterwards is up to you.