You talk about controlling your feelings. Feelings can not be controlled, but actions on feelings can be! You must control your actions.
Don't get me wrong, I am not trying to bash you. I understand your position from experience. I used to base my self esteem on that too. I ended up falling in love with another guy while I was married, but I did not act on it.
Counseling was going to be my recommendation, so I am glad you are pursuing that avenue. You need to recognize that you are a worthwhile person and nothing anybody else says will change that.
I have a few recommendations (I am not a professional councilor, but I believe this is good advice).
1. Start volunteering somewhere (a soup kitchen, local museum or zoo, a school, a youth group like Girl Scouts, a church group, or whatever). This way you can prove to yourself that you are a good person, you worthwhile and you are important to the community. If you don't feel good about one volunteer position, find another one that makes you feel important.
2. There is a concept in psychology call aversion therapy. One method for this therapy is to wear a rubber band around your wrist and "snap" it on yourself when you are thinking things you shouldn't. Examples of thoughts when you should "snap" the rubber band are:
a. I have romantic feelings for this other man
b. I am worthless
c. I hate myself
d. Nobody loves me
e. I am not a good person
3. Tell your husband that you have been basing your self-worth on what he and other people say. Ask him to help you find your own worth. (He obviously things you are very worthwhile if he is staying married to you despite your infidelity.) Once he understands this, he will probably be more than happy to help you.
Best of luck!
Doc