I got preganancy test positive on april 25 and got heavy bleeding on may 15 but my doctor said it was only a period?...

Could have : been a miscarriage, however, if the doctor's testing did not show pregnancy can be related to ovulation problems/delays, from polycystic ovarian syndrome/insulin resistance.

See below: It is likely that you had spontaneous loss of an early pregnancy, which is not uncommon. About 25% of early pregnancies are lost, mostly due to chromosomal defects in the embryo. Usually the only manifestation is a slightly heavy, delayed period. A common term (though cruel) for the phenomenon is chemical pregnancy. Wish you good health!