What Does Spotting Instead Of Periods Imply?

I m 22, maried for one yr. i m trying to be pregnant and i couldn for all these months, once i had miscarrage. now my doc put me on letoval. 2 cycles are over. i don know if i m preg. i hv got my periods now. its spotting.. doc asks me to continue same tablet. pls help me. wat shud i do??