Rather than applying effort to your husband and his relationships, focus on your own mental health. In this situation, you really need to worry about yourself and your child first and foremost. Your husband and his business will sort itself out on its own.
Find a good counselor and stick with it. Work through why you've allowed this to go on for so long.
And while you're doing that, find a good lawyer and file for divorce based on your husband's persistent infidelity.
Get yourself and your child out of that situation, continue counseling, and stay out of any type of relationship until you are divorced and your counselor feels like you are in a good place to start dating.
Exercise, yoga, healthy diet, find a new hobby where you can be around other people in a positive environment (a book club or something), find things that will help restore your confidence and self image while you work on yourself.