The betrayal means there are fundamental problems in your marriage that have not been resolved. The betrayal itself is a reaction to those problems. The very best thing both of you can do right now is to talk openly about the problems in your marriage until they are solved, including whatever it was that led up to the betrayal. Start talking with her about those problems now, and keep talking until they are resolved. That is key to having success with anything in the future. Bringing more people into your life now will divert your attention away from this. It will aggravate the problems in your marriage.
If and when there comes a time that your current issues are resolved, then see where you are with bringing others into your life.
It's not a good idea to give up something that you really want or need to try to make your spouse happy, so you can keep your marriage “at all costs”. If you do this, you'll suffer in the long term. That means your marriage will weaken in the long term. You mentioned she is putting pressure on you to let her do what she wants. That is not a good sign. This shows a lack of maturity, and respect for you. That weakens the relationship.
Originally Posted by kari777
The betrayal that I have to get over and learn to trust again
This is not about you learning to trust your wife again. This is about your wife learning to be worthy of trust.