J.G.
Sounds like just need a break! I get cranky, and feel terrible about it. Usually I need two things (1) a good nights rest --7 plus hours, and (2) a good 5 hours block without my kids.
You need to find a way to get out of the house alone. Sometimes I just run errands on teh weekend and leave the kids with their dad. That helps me get stuff done (which always makes me feel better), while getting a few hours of quiet. It's the noise that gets to me half the time. I just want silence, not the constant chatter of a 3 and 5 year old. Man do they talk a lot!