Since it's been a few weeks since your original post, I hope you and your doctors have managed to figure out the cause of your problems.
I had an ectopic in February, and the three original home pregnancy tests I took when I felt pregnant (slight nausea, swollen breasts, tight waistline) were somewhat inconclusive. The second blue control line was THERE, but faint enough to make me wonder.
My physician confirmed a pregnancy with a urine test in her office. Shortly after that, I had an excruciating pain in the middle of the night that felt like a labor pain. It went away, though, and I ignored it. I hadn't yet had my first OB/GYN visit which was scheduled for 11 weeks. Before that happened, though, I started bleeding vaginally...no pain really, but I was worried and went into the OB/GYN...they confirmed an ectopic via ultrasound.
They told me if I'd had a blood test to confirm the pregnancy, it probably would have been noted that my HcG levels were low and not really increasing much. This makes sense to me when I consider the home pregnancy tests didn't show a strong positive result.
My recommendation is to definitely have a blood test.