What should I do now that I feel that I'm not really in love with my wife of nearly 20 years?
Why don't you love her?
I'm just tired of her.
It's understandable to no longer be in love with someone after such a long time, but if you don't love her then you should get a divorce. It isn't right to stay with someone that you don't love anymore.
I will because it's not my fault. I'm not the bad guy.
Good, if you truly no longer love her then you should divorce her as that's the fair thing to do. It would be terrible if you kept her around in a loveless marriage.