Cheating is selfish and dishonest.
Need to discuss your unmet needs with her. She in turns needs to tell you her unmet needs.
Need to figure out what you can do about each others needs.
BTW - Witholding physical intimacy from your spouse is as wrong as cheating.
If you can not meet the needs, then discuss what can be done to meet them. Would you be surprised if she wants to play on the side too?