Spiceoflife - I had that same pain with my mc early this month. I had really bad O pain - from the area's around both ovaries (I'm guessing I O'd twice at this point), I couldn't walk, couldn't sleep, and had to take really strong painkillers and a heat pack just made it worse.
I then had stinging pain on the left side of my lower abdo (about 2 inches below and slightly to the left of my bellybutton) the day I went in to get a bHCG done at 11dpo, along with a temp drop, which 4 days later came back negative (the same day I had a positive HPT with 2ndMU) AF was 1 day late by this stage.
When AF was 3 days late I did another HPT in the evening, and it came up with a faint positive too. I had severe lower back pain that night and when I woke up the next morning (sorry TMI) I was bleeding with lots of black clots (day 1), had an extremely heavy flow for the next 2 days (days 2 & 3) with heaps more black clots, then one day of light flow with a few black clots which ended with spotting (day 4), then a bit of pink on the TP the next morning and nothing after that.
Took a week for my HCG levels to get down to 27, and another half week to be back down to zero.
You're not alone darl.
I also had a chem back in early January as well.
I hope that helps