Well, it sounds like your marriage was over a long time ago.
I dated a women who waited 10 years to get out of a bad marriage - WHY go on like that? She wwas miserable for 10 years - I think she cheated as well - when the real problem is she did not love her husband at all. It took 10 years of her life - now she is really happy. Joint custody - which will probably happen to you. My sisters exhusband cheated and he still got joint custody.
I know it's hard - BUT THIS IS THE issue - you need to either go to counselin gwith yor husband or end it. This is wh yyo ucheated.
Time to GROW up and take control of your life!