I am currently on day 11 of my period... the flow isn't heavy but every now and then it's like the flood gates open and theres massive clots (bigger than a half dollar) but then immediately goes back to barely spotting.

I'm not having any cramps, I'm not on any meds nor have I recently changed my meds. My cycle was very irregular for several years but this past year has been pretty on the spot. This issue, however, I have no clue what's going on.

Any ideas? I have an appointment on Wednesday with my doc, but I'm worried. I feel pretty fine other than mood swings, and my pregnancy test was negative.