Can you still be pregnant after having a light period?

I had a very very light flow period this month with no clots. I usually have heavy periods with clots. My Uterus feels very heavy and sore when we BD. I spotted for a couple of days ago after every BM. I took a HPT and it was neg. Plus I would be around 6 weeks now (counting from first day previous month's period) so I would think a test would show up by now.