WTF is going on???

I've had some very light brownish colored spotting since my HSG on Tuesday. This morning I woke up with a stain in my underwear around the size of a quarter. When I wiped, there was a lot of reddish brown blood - more like a period. So wtf is going on? I haven't had a period without provera since September, and I am only on CD 12. I put on a pad so I could try to monitor how much I am bleeding. I don't think I have a fever and don't feel sick (the things the doctor said to look out for after the the test). I hate my body.

The only good news is if this is the start of my period, I can't have an endometrial biopsy next Friday.

update #1: Just checked my pad and there was some blood, but not enough to change it. That makes me feel better because heavy bleeding could be a complication. There was a rather large blood clot, but I'm guessing this is all just related to the hsg.