My sister and I are both pregnant at the minute and frequently exchange updates on our "rages". She has hers in the mornings. Mine come in waves over a few days and are targeted at colleagues, my partner, my in laws (at least they deserve it) and even random strangers. I'm lucky to have someone close going through the same thing as it helps me not to feel too bad about it.
You shouldn't either OP. This is definitely a normal part of pregnancy, what with the hormones. A very lovely and gentle friend of mine actually threw her husband out of the car on the motorway, in a foreign country! Also, in your case you're in pain and not sleeping very well, and probably dealing with the endless annoying comments that seem to be part of pregnancy, and your own internal worries. Anyone would be irritable in your circumstances.
There are a few things that help me to feel better, which I'll share just in case. One is to listen to pregnancy relaxation exercises - you can buy them off itunes (I have Maggie Howell and Katharine Graves, both fine if a tad naff) or listen for free on youtube. Doing them at night definitely helps me to get more sleep, or if I wake up in a bad mood I do them before I start my day, and that makes a difference too.
Doing deep breathing also helps (in for four, out for five, repeat). The other day I got so angry I had to do it in a work meeting. I think some of my colleagues thought I was actually in labour!
And of course general relaxation is good. I try to minimise stuff I "have" to do at the minute (eg family obligations) and focus on doing stuff I like - long walks, going to the cinema, sitting in the sun etc. I also reserve the right to a duvet day now and again.
Last of all (and apols if this is the kind of annoying comment I was bitching about above) maybe you can get some help with the pain. From what I've read GPs etc don't tend to be all that helpful but apparently seeing a pregnancy chiropractor can work wonders.
All the best hun and if none of this works, just embrace the rage!