Hi,

I'm 20 years old and have usually been very regular when it comes to my period. It has always been very regular arriving on the day it was supposed to or a couple of days before. However this time I'm 2 days late already. Such a delay has only occurred once before around 6 years ago. I have not had sex but I have recently started exercising a bit and am eatling less. Could this be the reason behind the delay? Please help me out

Yes, it might be. Extreme athletes sometimes stop getting periods completely. Nature is conserving blood for you, and it makes sense. It helps prevent pregnancy in times of deprivation. But really, it is extremely rare to always get your period on a regular basis. A few days late, a few days early, that is normal. Plus you will change as you age.
I averaged 29 days until I had my tubes tied at the age of 28. I have no idea why my average was longer after that, and may never know.