I have first hand experience with this. 2 of my pregnancys i got a positive with a First Response. I went to the clinic where they told me they were negative and to come back in a few days. I came back and they told me it was still negative. So I went to walmart and still not drinking or peeing I bought a first response and a digital ept. They all came back positive. There is rarely such thing as a false positive. You saw a line it means your preggo. The tests at the clinic are cheaper and dont measure the same amount of hormone. Good luck