I hope dropping the T-Bomb went as well as to be expected. It is never easy for an SO. THe way I look at we spent a lifetime trying to sort it out and BARELY have a handle on it. Imagine how it must be having it essentially dropped in your lap!
The whole unknowns of totally defining the marriage, the image of who you are, the feelings of betrayal, being lied to. Feeling that "I should have seen the signs". "If I only knew I would never have...." are overwhelming. There are a thousand questions you cannot really answer. It's tough, for you both.
My wife and I after a good 5 years are still dealing with these issues. And she knew for over 30 years that I had GD. She thought I was "Just a CD", I saw it as CD++. Next lifetime perhaps I'll have better luck. But as you saw, it does not go away, only really gets worse if you ignore it.
What has kept us together is plenty of brutally difficult honest and open talks. (BTW- sharing such feelings and emotions were a totally foreign concept for me). Though difficult for me, I knew I needed to for the 'Us'. Difficult for us both was avoiding TMI. There are plenty of raw totally unfiltered emotions being let loose. The strength of the bonds of love for eachother will be tested. What is said must not be allowed to fester. Yet that time is not one for heated debates or lashing out being hurt. - Even more talks later.