Hello, My Last Period Was Jan 28th, Am Taking Folic

Hello, my last period was Jan 28th, am taking folic acid tablet since fab. Urine test was negative. My gyc suggest to take duphaston tablet for 5 days. We are trying for baby. I ve done all d tests like thyroid, hormone and pelvic scan also. Everything is normal. Wat is the reason for delay period, is there any effect for fetus using duphaston and my cycle is 35 to 40 days. Pls help me.