TTC after Tubal


I had a tubal back in 2007 and my doc had to go in and do emerg. surgery cause my tube exploded @ 7wks. I took a HPT on Monday morning and it came back with a BFN. Took another one later that day and got a BFP. Was shocked so I went and bought a 3rd test and got a BFN. Scheduled an appt with doc for Wed to get a blood test done to find out for sure if I am or not. Trying to figure out what would cause a false positive result.