Day 1 of your cycle is the first day of red flow.
If you got a negative on a HPT, it wasn't a chemical pregnancy.
As for the brown spotting, it could be several things...you may have irritated your cervix, you could have a cyst, it could be from lower progesterone levels during your luteal phase. It's impossible to know without talking to a doctor. I also get a few days of brown spotting before my period starts, but my luteal phase is normal (14 days) and I've had 2 doctors tell me it's nothing to worry about. See what your body does next month -- if it happens again for a week, you might want to talk to a doctor about getting your progesterone levels tested. There are also progesterone creams that you rub into your skin that you could use during the LP (provided you are *certain* that you ovulated) to support your progesterone levels. But more likely than not, it was just an "off" cycle and your hormones were a bit out of whack. See what happens next month. Hopefully you get a BFP!