Hi, welcome to SI. So sorry you find yourself here.
Trying to be brief bc I'm on my way out but just a few thoughts.
Infidelity is traumatic, it is going to take years to move past your husband's betrayal. Not weeks or months but years.
Marriage counseling is a waste of time and money. The marriage didn't cheat, he did and he should have an individual counselor as well.
Was it an emotional and physical affair? Has he told you the entire truth? Understand cheaters lie and deny and minimize, if there was daily contact more than likely it was a physical affair.
Then I have to keep quiet because while he is understanding he's also fed up of dealing with the fallout and wants to put the whole thing behind us.
I need to stop the self destruction
He's fed up? A truly remorseful spouse will handle everything they have coming, he dropped a nuclear bomb on your lives, he should be begging you to give him another chance, not get defensive or insist you get over it, be willing to answer every question you have repeatedly if necessary, give you access to emails, phone, social media, whereabouts at all times.
Rage is masking hurt, you just boarded this emotional roller coaster from hell, it's going to take a long, long time to manage the hurt, years to be exact. I raged like a freaking lunatic, became a potty mouth, my husband's affair almost broke me and changed me at my core for a very long time. It's all very NORMAL. You are not self-sabotaging, you are trying to process this living hell your husband brought into your lives.
Has he given you a written timeline of the affair?
Also, he should not be having ANY contact with this colleague. None. Ever again. My husband had an affair with a co-worker who worked at another site 3,000 miles across the country, there was no way in hell I'd tolerate any contact with her, even professionally. I insisted he find another job, and he did because he understood he could no longer do his job to the best of his ability. He gave up a 25-year career.
BTW, is this other woman married? If so, her husband deserves to know he is living a lie.
Please don't ever share this site with your husband, and if the other woman is married, you should tell her gently with undeniable proof. The best way to end an affair is to shine the light on it. Never, ever inform your husband if you decide to do this.
There are two good books I suggest your husband read, How to Help your Spouse Heal from an Affair by Linda MacDonald and Not Just Friends by Shirley Glass.
Weekends are a bit slow, others will be along to support you.
Again, so sorry are dealing with this massive betrayal. A big virtual hug to you....