You are the third person I have ever seen talk about this. Me and a friend from lauras was talking about this same thing a while back (Oct. 2011) Exact same thing happened to me starting the 3 or 4th month of hrt. To her I believe it started around the 6th month. Same exact problems and conditions. She -was- looking into it. Her doctor had ruled out pretty much everything. By everything I mean, kidneys,liver,thyroid, appendix, hormone inconsistency, blood levels,blunt trauama lol.
Literally a lot of things. PMDS seems to be a pretty good start though. My doctor said she would do a sonogram and such if I felt that it was something I wanted to look into. Of course I would like to know exactly what the heck is going on with my own body, but funds are kinda limiting that at the moment. Either way, its not common. At least in the trans circle of things. Out of 7 months of searching about this online, I haven't seen much about it. I see the common "headache, moodiness, emotional" from those who are on progesterone if they cycle it, but for those who don't and have full all out period (minus the blood)...not so much.
If its allowed I could link you to the discussion we had at LP's if that is acceptable?