BFP followed by an indent

Okay ladies I need some opinions. Yesterday I took a test with a dollar general cheapie and got a light, but there positive. Today I wanted to follow up with a FRER to see if I’d get a darker line (because FRER is the only test I had). As soon as urine hit the strip the line went from pink, to white to nothing in a matter of 10 minutes. So do I say I’m pregnant or not? What’s going on?? I’ve gotten nothing but indents from FRER. I need help. 🙁