AF or possible IB?

So, I really don't remember much from the beginning of my first pregnancy. I'm 12 dpo today and cramping like crazy. It's not painful, but I feel wiped out and it's -there-, yanno? Noticeable. Anyway, yesterday I spotted brown, just once and I don't usually spot throughout my cycle... AF just shows up to ruin a good time, there's no pre-show. According to glow AF is due on Tuesday... Is this the beginning of that nasty bitch or could it be a little nugget of love judging by dpo? I think I vaguely remember spotting once with my son too,  it's all very fuzzy.