Dear Nidhi if your cycles are regular then ovulation in a menstrual cycle occurs in the middle of the cycle,
and a few days on either side is considered to be fertile period. A person can get pregnant if she has sex in
the fertile period. As your cycle is of 28 days your ovulation will be around 13-14 days ,so 7th day doesnot
coincide with the fertile period and chances of pregnancy will be less. Delay in menses can also be due to
stress, hormonal imbalance, imbalanced diet, depression, thyroid problems, poly cystic ovarian disease etc.
Get a pregnancy test done to be on the safer side. Take care.