false positive?

Loretta
I had been feeling off after getting a short light 2 day period and decided to take a first response test thursday. 
My symptoms were just tiredness, foggy brain, insomnia, gas, and constant light dull cramping. It's like a constant light rumbling down there. But no nausea or vomiting. 
I took the first response test at the end of the day Thursday ( negative result) and it was my last test so I went out and bought more, but I bought a digital test since I thought maybe it would be easier to tell. 
I tested the ept digital test first thing the next morning and it said "pregnant". I thought maybe I got a positive because my urine was more potent, so I decided to try one more red dye test (same as first test) and waited till I had to go early in the morning the next day (this morning), hoping it would be more concentrated. 
Well, I still saw no positive line, so I don't know what to think.
I've heard digital are more sensitive, but the first response rests get tons of praise for accuracy.
Any advice?