Ok so I am 26 getting ready to be 27. I have never actually tried to get preganat but I have never tried not to. My boyfriend and I have unprotected sex and I was late one week starting, I thought I was pregnant but I guess I'm not. I wasn't stressed and am always within a day or two of my period. Does anyone have any ideas as to why I would have been that late?

A "normal" cycle can be any where from 19 to 30 days. So, a week off is still in the normal range.
Are you sure you weren't stressed about being pregnant? Sometimes our minds can trick our bodies.

You can always contact your doctor and just get a check up.

There are tons of reasons a woman can be late or skip a period, aside from pregnancy.

Stress
Physical Excerise
Weight Training
Overwieght
Underweight
Schedule Changes
Illness
The list can go on and on