If you are underage and were underweight before pregnancy, what are the chances of going into labor before the due date?
Anna, this kind of thing is very unpredictable. Keep going to your doctor's appointments and take care of yourself.
The chances of having premature labor are determined by various factors and hence it is not clear cut in your case. You should go for tests to accurately determine if the pregnancy is healthy and there is no risk of premature labor.