Age does make a difference because with age comes more life experience but I would say what I am saying here to anyone.

You make excuses for her cheating on you because you were away?
You are willing give up sex forever for her to stay with you?

IMO.... Your are being treated no better than a doormat and what is even worse is that you are apparently willing to let her.

A relationship can be healed if both parties are willing to form a union and work on it. Trangressions can be forgiven. Hurt feelings can heal but, if only one person is working on it then it is doomed.

Your first loss of esteem happened when she cheated and it appears that it continues to erode so, maybe you should take some time for YOU and think things through. Maybe go talk to someone impartial who can listen without opining on what you should do. but teach you the tools to help you get through this rough time in your life.

AND of course you can take what I am saying and not give it another thought!