J.W.
I will tell you, and this isn't the only reason but the breaking point, that stress, with no one to support you, was the final nail in my marriage's coffin. You need support!! Find it somewhere.
I know some other moms who had or have kids in Andy's school. Any one of them would take Andy for hours if I asked and I would do the same. If you have raised one of these kids you know two things. Adding one more doesn't change much and you know the value of support.
I can promise you, and this may sound bad, the only way you can get down time is away. No matter who is there to help you you will always respond because they are your child. If you hear them you will take care of them, ya know?
You will eventually learn how to redirect, then going out won't be so bad. :)
Sorry if I rambled a bit, I need to get off of the computer and relax myself, the kids are at their dads.