J.M.
false positives are very rare, especially if you arent on fertility drugs, which i assume you arent.
i dont know why your doctor would suggest to keep taking the pills and retest. pills dont affect a pregnancy test, and although they say the pills now shouldnt hurt a fetus, better to be safe. if it were me, i would get 2 more tests today. take one today, if negative, take the other tomorrow am with first urine. if either shows positive, i would say you are pregnant, and call the doctor to ask for blood test. tell them you are concerned since you were on the pill, you are unsure of when this baby was conceived. its very important to date a pregnancy correctly for measurements and the heartbeat, but being on the pill, you cant be as sure of conception. good luck, not sure how you want this to go.
ETA- i would use condoms though as birth control until this is sorted out, then if not pregnant, just start a new pack next month.