Actually you can get a false positive if you read the test a long time after you are supposed to read it due to the reagents in the test.
However if it's a line, however faint, after the 2mins or whatever it's definately positive!!! My hubby made me do another one when I got home and told him - don't think he believed me! 3 positives is DEFINATELY a positive, which is what your GP has proved

yaaaay!