What Could Cause Delay In Periods,spotting And Light Cramping?

I am currently 4 days overdue for my next cycle. This morning at 6:40 I took a digital first response pregnancy test and it said YES+ and when I wiped I saw light pink blood but definitely a lot lighter in color than a normal period and not as heavy but not spotting either. My husband came home for breakfast and had me take the other test which was a line test. I took it at 8:40 and it said no. So I immediately go to my doctor at the hospital on base and give a urine sample. It was negative. The only things I can think of either I got a false positive or I took tests too close together. Now I m still bleeding but it s lighter in color and I have very very light cramping? Could I be pregnant?