If i have sex 20 days after my period i can get pregnant?

Unlikely: It depends on how you define the numbers. Day 1 is the first day you bleed. If you have a 28 day cycle you might be most fertile at mis cycle (14 days) if you have a longer cycle like 35 days, then your peak fertility might be 18-19 days. If your 20 day calculation begins after you stop bleeding then you are ven less likely to get pregnant.