I'm a 20yr old girl,, my menstrual cycle z always 28days,, and i had unprotected sex on the 26th day,, should i worry of cases of pregnancy?

Hmmm....: Unless a woman is trying to have a baby, she must not have sex without a reliable form of contraception. If she has sex, she should take an emergency contraceptive pill right away if not married, settled down, and ready for a baby. It's known as a morning-after pill. Day 26 (in a 28-day cycle) is not a fertile day, but young women having sex always have to be ready for a cute "surprise baby."