First time i had period was about 6 yrs ago.it was irregular at first but then it became regular.not sexually activ.this month my perid is late 7days?

Not highly unusual: Emotional upset, weight loss, excercise or a hormonal imbalance (female hormones or thyroid) can cause a change in menstrual cycles. If you have not been sexually active, pregnancy can be eliminated as a reason. It's probably best to watch the next couple months to see if they are regular again or not. If not it is best to see a doctor to evaluate further.

Period: This is a fairly common complaint. Presuming you have not had ANY sexual activity in the past 30 days, you should just wait. Skipping an entire month is not that abnormal for some women. If you go 2 months without a period see your OB-GYN and they may draw some hormone levels. A birth control pill is often used to 'normalize' periods.

Any health change?: Overly athletic? Recently sick? Stressed? New medications? New diet? You can make an appointment to see your primary care provider or gynecologist if not resolved or if having pains or other problems.

Irregularity: Especially given that you're not sexually active,I would have to assume it's your body having an irregular period,meaning that your hormones may be just slightly off this month.This is not an uncommon event and happens to many women during their lives. If you are not experiencing any vaginal discharge, pain, or lower abdominal discomfort, wait it out. If prolongs beyond 3-4 weeks talk to your doc