I'm a breastfeeding mom and my son is 4 months old... I was suppose to get my periods on the 5th or before than but I didn't get them yet... we alwayz use condom as protection .could it be possible that due to breastfeeding my menstrual cycle is disturbed or am I pregnant again?

Breastfeeding can alter your cycles. Had they returned to normal since birth and have just been irregular or have they not been regular since birth? How often are you breastfeeding and is he getting any supplementation?
Pregnancy will be a possibility as well, so give it a few more days and try a test if still no period.