I've been spotting for almost 3 weeks. It started around day 15 or 16 of my cycle, so I thought maybe it was ovulation bleeding but it just kept going. It is very light, barely noticeable. I don't know how long my cycles are, because I take a while to regulate after having a baby (I've had 2 periods since my son weaned at 8 months, he is now 13 months) so I don't know if I'm "late" even though based on a 28 day cycle I was due for my next period 4 days ago. I've taken several pregnancy tests which have all been negative. Any thoughts?

I think its probably just that your body hasn't finished adjusting yet. 13 months is a long time but its possible if it is just very light spotting that your body is just finishing its adjustments? It doesn't sound as if it would be anything harmful to your health. However if it continues for more than another week I suggest making an appointment with you gyno.