C.,
I was about to respond privately, but I thought there may be another mom out there who needs to hear this too. Please read everything before you act on any of it.
I have had very similar experiences over the years (my kids are now 10, 7, and 5) and wondered if something was wrong. But I always brushed it off and went on. Things really got worse in the last 2 years, and I tried to ignore it, but the self-recrimination got aweful and then my temper got worse and .... bad cycle. I got really depressed. Finally I went to the doctor (I tried 2 years ago, and chickened out, so last winter I made my husband go with me and talk to the doctor). The family doctor tried to treat me, but quickly realized that he didn't have the expertise and sent me to a psychologist. Turns out that I have bipolar disorder - and I have probably had it since I was a teen! (btw, I am not Bipolar, I am a human with bipolar disorder - verbage can be very important!) It has been a hairy year, but we got medication at the right dosage and plenty of counseling and I am able to be a MUCH MUCH better mom. Yes, I still get angry and frustrated, but I don't loose it like I used to. And when I do start slipping up, I can back off, cool down, and stay in control.
I'm not saying that you have bipolar disorder, or any other mental illnes. My example is probably extreme. But what I am trying to say is, if you feel like you might need help, like counseling, get it. I won't hurt, and it could certainly help. Most medical insurances have a 'mental health coverage' that can help towards costs. You can also go through your church if they have anything available (LDS social services is good, and they charge on a sliding scale). Think of it this way - if you were worried that something was "off" with your child, you'd probably take him to the doctor. Trust your gut about yourself to. They may just set you up with some parenting strategies (who knew kids didn't come with an instruction manual?), or give you whatever help they see you needing.
Hang in there. It can be tough being a SAHM, especially when hubby is gone a lot. When you beat yourself up for mistakes, you end up even worse. There is a solution, and there's no shame if you need to ask for help to find it!