Disappearing positive line.

So I took a First Response Early Result test with my first mornings urine I'm about 12-15 dpo I think & I took the test & let it sit than at about 3 minutes I saw a faint positive (picture at the bottom) then minutes later it disappeared leaving me with a negative, I've been taking other test & getting weird positive results after the time limit, I'm so confused & idk what to think. this is my 1st first  response test before I was using cheapies.