I don't think you are pregnant. What you are describing does not sound like implantation bleeding (which is largely an Internet myth anyway) and you took all your pills, and your pregnancy tests all came up negative. Short of a signed confirmation letter from God, you can hardly have a more sure profile of someone who is not pregnant.
Why are you running your pills onto such a long cycle? My guess is that your body is trying to tell you that it thinks you should have a period.
That said, having a little bit of bleeding
It depends on the test's sensitivity, but I would say it would even with a relatively insensitive test. I assume you followed the instructions and tested with concentrated urine (the box usually says to use first-morning urine). If you used an "early results" test you can trust the answer.
In your shoes, I'd take the blood as a hint it's time to have a period, and stop the active pills and take the placebo pills, and then begin the cycle all over again. You could talk to your doctor about it if all of this three-month stuff is being done on his or her recommendation. But if you are just doing it on your own, my point is that breakthrough bleeding is sort of a hint that it's time to give yourself a period.