Okay, this is my opinion on what might work for you. These are the things I had to do when I was a struggling, single mom.
TAKE the alone time you need, when you need it. Don't wait for anyone's permission.
Lock yourself in the bathroom, and take a LONG bath. (Take a radio in there, and listen to your favorite music.)
Take the kids to see a movie. (Take your knitting, with a pair of those needles with lights at the points, so you can knit during the movie.)
Take the kids to the park, and take your knitting so you can sit down and relax while they play.
Work on yourself, by reading self-help books, or exercising, going for walks, etc.
Don't worry about the house being a mess. Just let it go, and concentrate on the things that you need. You're a working mom now, so the house will not look as nice as it did before. Just chill, and relax a bit.
Make a list of things you want to do in your life, and go about DOING them.
Have fun, because you only live once. Make it a HAPPY life!