Infidelity Support Group
Any relationship in which one partner engages willfully in sexual relations with another outside of the partnership is considered to have experienced infidelity. This breach of trust is often traumatizing for the faithful partner as well as the relationship, and support is often needed to heal emotionally and to decide whether or not the relationship should continue after...

Ask her what she wants. You sound dissatisfied, but she is, too. There are other ways to be intimate, hugging, kissing, massages. Be creative!
Cheating on her is NOT the answer. She is frustrated too. Work with her to come up with things to do that you BOTH like. She will be much more receptive to you if you are kind, loving, romantic. Be kind and patient and do loving gestures for her. She will be much more wanting to do something sexual with you if you are not being forceful or mean or demanding about it.
Women get turned on starting in her brain. Say kind and loving words to her. Do not be mean, forceful or demanding at all. Do nice things for her. Help her with housework. Bring her flowers. Take her out to a nice dinner. Romance her.
Has she said if something changed with her or happened with her, 2 years ago?
I still say you don't give up. Women "say" things, but we often mean something else. That we *would* want sex and intimacy, if this, this, and this were different.
Consider waiting for something she likes, perhaps a dinner, and then before you're about to go, then say, sorry, I'm not in the mood to go. I need you to respect my wishes. She will probably be mad, but this may start a discussion about what's really bothering her.