Not really. Often your period can be delayed a day or so by sex. If you haven't had a period in several weeks take a test.
yes
Most often, no. The supposed "normal" length of a menstrual cycle is 28 days but most women will have shorter or longer cycles.
from the age of 7 to 14
Two week
you are not supposed to have a period if you are pregnant.
It's possible. Stress can cause ovulation to be suppressed, but that would've been two weeks before you were supposed to get your period.
how AM I SUPPOSED TO KNOW jeez
Yes
There are doggie diapers that you can buy and have your dog wear.
This is common.
Yes your first period is supposed to be a very light one.