Possibly pregnant, but. . .?

I am two weeks late, but have been spotting - I did have some spotting in my first pregnancy aside from implantation bleeding, but not like this. I have taken a couple of tests, they have come back negative. The kicker is that my husband, my mother and I would ALL swear I was pregnant, and I felt like I "knew" before I took the tests. I have heard that some people don't test positive for as much as three months into the pregnancy. Has anyone had a similar situation and would I be crazy to go to my ObGyn for a blood test?