Insert a little black cloud right above my head...

I've been a wretched, nasty, mean and super agitated wife and mother lately and I'm ashamed. I really want to change, and every night I go to bed thinking about how desperately I want to change, then the next day comes and it's the same thing all over again. I'm just a grump. The morning usually starts off well, and I make it through the main part of the day okay, although I feel like I distance myself from my kids in order to do it. Stick to the schedule, get done what needs to be done, stay a professional {because of the daycare}. Then the evening {and weekends to be prefectly honest} comes and snappy mean mom comes out. I start feeling behind and burnt out and frustrated and just generally tired. Tired of the non-stop cleaning, tired of the non-stop reminders, tired of breaking up arguments and bickering, tired of correcting behavior, tired of preparing meals, tired of all the noise... really I could go on and on. Why am I in this negative place. I can be an anxious person, I've had to fight that my whole life, but this is maybe more depressed or something. Maybe I need to get my thyroid check. Or just get more sleep instead of staying up late enjoying a little time with less demands. Why can I not stay focused on the positive for more then two seconds? Why am I not enjoying my kids more? Why do I want to run away? {Not for real, just in my head...} Why do I feel so overwhelmed all the time? I want so desperately to be a better mom, and I feel so frustrated with myself because I feel like I know what I need to do but I just don't stick to it. I need to be more loving, I need to spend more time just being with them... I know that sounds funny coming from a stay at home mom but I get so caught up in taking care of the house and all the other day to day stuff, and the daycare that I forget to just stop and really spend time with them. I want to change my attitude so bad, I act stressed out and frustrated way to much. I want to appear {and feel} relaxed and happy more often. How do I get there? I want to be a mom that really enjoys her kids, and hardly ever raises her voice, stays calm and collected... has fun, acts silly and lightens up the mood in the house, and I want to be that mom on a regular basis. With out my house falling apart while I'm playing... I really wish I didn't care about that part so much but I do. So I guess I need to make keeping the house clean fun as well, know how do I do that?