Awww, Kim - I'm so sorry you're going through this again.
Step back a bit and take a breath first.
First - it does sound like there are tons of stressors (financial, the parents, and yes, fair or not, you "letting yourself go"). NONE of it excuses him having an affair, but it does make it more predictable.
I guess you have to ask yourself - is he a basically good guy who just gets weak in times of trial, or is he a serial cheater who can't be trusted?
I think it's smart of you to get some legal advice - just to see what your options will be. And at this point, you may want to be careful about your moves - ask yourself before saying or doing anything, "Will this get me closer to my goals?"
If your goal is divorce and being free of a cheating spouse, then you may want to keep quiet and not show your hand while you get your financial ducks in a row. You may also want to squirrel away a little emergency escape money for yourself.
Are you caretaking his parents? If so, I know it's a really difficult position, but you need to start thinking about getting work that can support you and your kids in the future.
If, on the other hand, you think you'd be willing to take him back, you may need to shock him out of his fantasyland. Seriously - what would he do if you left with the kids?
