dear dr. my periods come only 3 days, i have some problem to conceive, my doctor to prescribe me Letrozol tablets, when i visited this dr, on 10th November, my periods date was 6th November, then Dr. told me i start this tablet on 4th day of my periods. my question is that, this is important Letrozol tablet should be taken on 4th day of periods or 2nd day or periods.