Not a good mother

I have resigned to sitting in the bathroom with the fan on to get away from my children tonight.  Craig keeps on getting home exceptionally late, which leaves me to deal with these kids all day and all night, and having started this weekend with a 30 hour stretch of being awake, I am tired of everything at this point.  I'm not "PMSing", this isn't hormones getting in the way of clear thought.  This is just exhaustion.  And I'm pretty sure that I'm a horrible mother, so even when I try to do things right I know in the back of my mind that I can't, I'm not cut out for this in the first place.  Oh, sure, I can put on a happy smile and make a cute cake for a birthday and play tag once in a while and my kids seem to like it.  But in the hard times, when i've asked for something again for the 15th time, when all I want is alone time and Connor won't stay in his room, its in these times that I know I'm no good.  I hate myself in those times, because I have no self control over my words, and sometimes it is literally shaking me how hard I'm trying to control my actions.  All I want to do is swear and kick stuff, and I don't think that's a good way for a mom to be.  I've bought books an how to do this, I was a child myself so I have a little experience with how to raise a kid, but I'm beginning to think that a part of a person has to actually be skilled in this, and its a skill I completely lack.