I knew I should have said no when my husband proposed
What was your reason for not saying no if you felt this way?
I was young and he was rich.
It's okay if you want to end an unhappy marriage. Staying in the marriage won't be good for either you or your partner. Maybe you can discuss these issues honestly with your husband to avoid future unhappiness.
If a rich husband can't be faithful now, who's to say he wasn't going to be unfaithful before?
If you feel you have doubts about your marriage and you are not happy, you are free to get out of it. Nobody is forcing you to remain in a relationship you do not want to. The first step may be to try and work things out between yourselves though.