What if I want to share my wife?
That sounds inappropriate. How does your wife feel about that?
I'm aware that she is sharing other men too. I have tried to discuss this with her but she doesn't seem to understand my feelings.
Open relationships are complicated but as long as both of the people are okay with it then it should work okay. But if your wife doesn't want to listen and understand how you feel this will not work out.
I know she is seeing other men behind my back and that she is cheating.
If you and your wife agree to an open marriage then it is fine for the both of you. However, you can also let your wife know that her behaviors are unacceptable.