Can she not show you affection to you in any other way then intercourse?
It doesn't need to be sexual in any way.
Also, if your partner is not into it, shouldn't you give it a bit more thought? Maybe there is a reason behind that.
Have you tried asking her about that topic? Who knows what bothers her.
Sometimes "doing the thing" can be painful.
Just ask her.
And no. It's not cheating. But you really shouldn't talk to strangers when you are needy.
Especially if you are in a relationship.