Must, You can only fight your demons and issues not his also. Going to counseling is a great first step and will help a lot. His feelings for her will obviously make you angry, hurt and probably a zillion other feelings. However you cannot control his feelings or actions only how it makes you feel and react.
The ultimate decision is up to you. Do you forgive and move on with your H or if you are not able to then move on yourself. I do know (as you probably do also) that if you choose to forgive him you must do that and not bring it up. There is a lot to recover from before you get there Im sure. No one can make your choice only you.. I would work on yourself and give it some time if you are unsure. I dont believe that you are making a bad decision to consider your options for a while first. His depression is also something you cannot control. If he chooses to help himself that is wonderful however you cannot force him. He must follow his own path and his choices decide where his destination shall be.
I would recommend also implementing the DB techniques of GAL and do some 180s. You might surprise yourself on what different perspective it gives you to your own behavior.
Good luck! BTW it is okay to be a mess just dont let him see you!
______________________________________ H:32 W: 35 M- 11 Tog- 13 D-5 S-9 Sep. June 5th Bomb 6/27/11 OW Discovered on July 18th and admitted.... Divorced 11/22/2011 Ex Engaged to OW Jan. 2012