My fiancé is an immature selfish brat

I've been with my fiance for about 5 years now and I have really been wondering whether this is the right person for me. We are in couple's counseling.

He is a momma's boy and very clearly spoiled. He will complain about the tiniest things (like driving makes his thigh hurt because he has to keep this foot down on the pedal) and is frankly a brat. He's small-minded, will do whatever his mother says, lets her control EVERYTHING, and is extremely self-centered. Our therapist has been trying to work on these things and is failing because he can't seem to retain anything for long.

I'm wondering how long to give him before I give up. We're getting married next year; I still have time to call it off.

We are both in our late 20s. I feel like I wasted a lot of time trying to make this work if it isn't going to work.

Ladies, do men like this ever change? It is such an internal struggle for me.