That's a question for your doctor.
Go to doctor
If you want to avoid pregnancy, you should keep taking the pill.
if you havent missed your period than you are most likely not pregnant, but there are such things as false negatives on pregnancy tests and around 2 months is the time frame for those to be common. The symptoms however, you normally wouldn't be feeling most of those this early in a pregnancy, it could be your diet causing the problems. You should go to a professional for a pregnancy test if you think your pregnant.
It may be your birth control if you are taking any they cause irregular periods.
Contact a doctor. Sharp pains can be a sign of severe problems, such as an ectopic pregnancy.
there is always the possibility of a pregnancy if you are engaging in sexual intercourse. Check with your doctor, or take an at home pregnancy test
At 18 you must know how babies are made. If you have had unprotected sex, of course there's a risk for pregnancy. Take a test.
Chances are Good. In fact you may already be pregnant, which is why you aren't having a period.
9 months
Periods come and go, I wouldn't worry to much :)
a trimester is 3 months of your pregnancy. there are 3 trimesters in a pregnancy. 1-3 months, 4-6 months, and 7-9 months.
The first two months of pregnancy are the most important months of the pregnancy. The heart, brain, and other vital organs begin developing.