Oh googley, sending hugs your way! (if you'd like them)
I can relate to irritability coming with depression, and the frustration that comes with it. All I can say is, hang in there! Personally, whenever I start to feel this way, I try to do something that involves me being ALONE, so I won't be rude to anyone and regret it afterwards. (ie, listen to music, take a bath, take a walk, etc.)
Remember though that these feelings of irritability DO pass, so if you keep holding on, you can beat them. :]