Lately I've been finding that I don't find my wife attractive.
Why would you not find your wife attractive?
Because she is a big-boned woman.
It is common for spouses to lose that physical infatuation as time passes, but you shouldn't treat your wife as if she is not attractive.  You would hurt her if you said something like that.
I don't care. I'm sick of my life and I may hit on other women.
If you're having this many problems with her physical appearance then I would recommend seeking marriage counseling. This could help you find other things to focus on your marriage and stay happy.