As far as being me being "pissy" I would have to say all of the above answers you provided. Yes to justify her R with OM. Yes I have on occassion made statements that unintentionally came across as "pissy" yet would soon thereafter clarify / apologize to whomever, and Yes when I originally discovered the first text between her and OM I blew up (not in Amy form of aggression towards her). In fact, at that moment I told her to leave me alone. There's maybe been two other times my anger ever got that bad throughout our 10 years together. So all in all, it has been one of her complaints too. I also have to say that my moments (not excusing them) are magnified by her being in a DB R in her first M.
Today all in all was good, if not great. In the morning she followed me around a little and said she was "aggravated," and then paid me an "underhanded compliment" in the sense that when we have / do argue (which until now has been seldom) that I can be intelligent and understand her POV. So I thanked and that must mean she and OM are having another spat. At one point while we were at the zoo, she actually told me that OM was "pissed!" That we were together. My polite non sh*t eating grin / response was, "well, you are the mother of my 3 kids". And left it at that. So we finished the day fairly well on good terms thus far, she left for Zumba for about an hour, so we'll see.