I can't help it..I'm sexually attracted to my wife's sister?

I really can't help myself and I'm admitting it on the internet. I love my wife, but her sister is just SOO HOT it's unbearable. She always flirts with me at family get togethers and there was a time when we were both pretty drunk that we made out together. She said we shouldn't ever do it again, but I have serious urges too. She sends me texts sometimes that just says, HI and it drives me nuts. I'm trying to keep this super hush hush...but I don't know. I don't want to get a divorce cause then I'd lose the house, have to pay child support and what not. How do I curb my irresistable desire to sleep with her sister?