I am a 22 year old female. i have no serious health risks. i weigh 113 and am 5'3". My period is three weeks late and I am not sexually active. It has been irregular for over a year. I skip a few months and when I do get it it is very heavy. Although in 2008 I lost a total of 45 pounds I dont know if that is the reason for the late starts. I do keep my laptop of my lap a lot. Could that be a reason?