Hi Lost, I am sorry you find yourself here, but its a club full of very sympathetic and caring members, so welcome.
I dont have much advice for you, just wanted to say you are not alone and to listen to the great advice you will get as it really will get you through this journey you are now on.
My h told me that he did not think our marriage had been right since we had our youngest son 21 yrs ago and he just hung in there hoping it would get better ! Now he tells a different story, in fact does not remember saying it. They will say and do anything that suits them at the time, its all about getting out and living the fantasy that they have built up in their heads - the better life they feel they have and are missing out of. Reality is that once the shine has gone they will look at the destruction they have caused and be completely baffled how they got themselves into this.
You sound like you are a strong and independent person, that is a great start to gaining back control of your own life, as this is what this is about - YOU. I suggest you read all you can on MLC and depression, read threads here and post on them. Ask questions, vent or just tell us about your day, the good, the bad and the ugly.