I had my period last month and it lasted for 11 days but my normal perid cycle is 3 days and now im delayed for atleast3 days?

Not unusual: Always consider possibility of unplanned pregnancy if sexually active. Especially at your age, however, having an occasional irregular cycle is not unusual. This is usually due to your body not ovulating one month, and throwing off the timing of normal cycles. If you well and are not pregnant, wait and anticipate your cycles will go back to normal.

Probably temporary: Most women will experience occasional irregularity of their menstrual cycle. If it persists, and you are not pregnant ( obtain a pregnancy test), your gyn will probably want to check your thyroid and prolactin hormones and perhaps order a pelvic ultrasound and some additional lab work. Again, this pattern will prove, hopefully, to be a temporary problem. Good luck.