Okay, listen. Doesn't matter if he's gay, doesn't matter if he's asexual, doesn't matter if he says he's straight. He doesn't like vaginas. HE IS NOT STRAIGHT. And the sooner you accept that fact, the better. He is not into what you have downstairs and unless you can accept that you're marrying someone who will never satisfy you sexually, you are in for a really bleak future.
It would be interestin to see what he would say if you told him penises are slimmey & are unpleasant looking? Then see if he changes his attitudes?
Everyone goes straight to the gay idea (ok that sounds odd...) but in reality that is not the only option. People get odd hang ups about odd things, and unless he is willing to talk to you or someone else, there is no real way of knowing. He might be hiding gay tendencies or thoughts, or he could have had something traumatic happen, only talking about it will tell you for sure.
It sounds like he is either gay or asexual. Either way, it is problematic. I highly doubt he is straight or bi. I am bi. I LOVE sucking, licking, fingering, rubbing, and fucking pussy. If he is not attracted to the female genitalia, then he is either gay or asexual. It's that simple. You said in one of your comments that "he identified as being asexual before," so I am guessing that he is probably asexual. If he is asexual, accept a sexless relationship, break up with him, or ask him if you can have a non-monogamous relationship. That's really all you can do.
In a way, vaginas are icky and slimy and gross. depends on his taste and on your body. you could try making a fetish out of your vagina. or get him to fantasize about it instead of jumpign right to physical usage. fantasy is a way to make him want something. think visualizations. think of putting the image of your vagina into a fantasy that he already likes.
or coat your vagina in a food or spice he likes. or let him draw and paint on your vagina, to get comfortable with it.
Put the marriage issue on hold....Please do not marry this person.....hang with him but keep you eye out for Mr. SuperFreak. It's much better being married to someone that REALLY digs sex than someone who is lukewarm at best.