Mostly, a positive means a positive but I'd suggest that you should go for an HCG blood test. Bloodtests are much more reliable than HPTs. Or if it's not possible then go for another two HPTs to know for sure.
if its the blue tests they suck and give alot of false positives and you should try a first response early test and its a simple single line or double line its not blue dye and very accurrate. I would test again but they say if its a positive before the time frame is up then its a def. a positive....
If it showed a positive in the proper time frame, you can assume it's a positive. False positives are extremely rare, and they tell you to not look at the test when it's outside the time frame because of evap lines. If you're still not sure, you can get a digital readout test. It would take the guess work out of the lines and would tell you in words.