Last month I had my period just for two days although it was heavier than normall, now this month I am 3 days late on my period normal dates or 5days late counting I just got my previous period for 2 days, pergnacy test showed necitive but could I be pregnant?

How many test did you take?
Sometimes they can be inaccurate so I would suggest taking more then one. But the only one to be 100% sure is to go see a doctor.

Yes, false positives are not uncommon
But also three days is hard to say you are late, many women are give or take that many days all the time.
I would go about one more week, if no period, take another test, be sure it is the first urine of the morning.
If still nothing time for the doctor to check on it