Will,
You have to do what is best for YOU!! Staying with a woman that cheats on you Physically or just by having drinks and showing interest in ANOTHER man is BETRAYEL. It is very bad for a persons self~esteem to KEEP hanging onto someone that does this. A person that can keep doing this to their partner doesn't even know what love, loyalty, or marriage is about. Think about what you really want. YOU can't CHANGE her. You have developed a pattern and let her take advantage of your being forgiving and good natured. Probably was time to put an end to the relationship a long time ago.
People ALWAYS have a hard time with CHANGE and divorce is a HUGE change. Makes people uncomfortable. I would Highly recommend you Buying a book entitled "SELF MATTERS". Read it. It will help you to learn why you have allowed this, who you really are and also help you to figure out what type of person that you want to share your life with.
GOOD LUCK!! Wishing you all the BEST!!!!!!!