While of course I do not know what is actually going on with you personally, what you are saying reminds me of depression I experienced recently. It was mild and maybe partly situational. I needed to kind of get out of a funk at work related to a project among other things. Hard to say what caused what as I had a hard time concentrating so maybe that was the cause of the difficulty at work. I do get a bit irritable when depressed, too. If you think it's depression and it's mild maybe therapy or lifestyle changes could bring your mood up a bit. Since you're noticing it after a med change seems like a good reason to talk to your doctor.