ladies, why do I keep getting faint positive?

I am BC, not TTC. I felt pregnant 2 weeks ago, took a test...positive. That day, I got a blood test after calling my doc. Negative. (I also had a negative blood test when I WAS pregnant with my daughter...2 weeks after conception)
Fast forward 2 weeks. I still feel pregnant. FRER keeps saying positive. No bleeding and cramping in between. So not a chemical pregnancy. No period since January. 
Dollar store tests come up negative. FREE shows faint positives. To see if it was faulty, I even had my husband pee in one...straight negative. 
2 weeks and still no dark lines in FRER. 
Why/!? Any idea on what's happening?
I feel pregnant and fear that I am.