Skipped periods?

I have no had my period for over 3 months it is not pregnancy as I have not had sex. I have lost a lot of weight recently and im noew slightly underweight. Could that be why I havent had my period in so long? ( almost 4 months)

You're young your hormones are still trying to get right. Being underweight can cause your periods to be irregular or stop all together. I have never had a regular period so I got put on birth control to try and regulate them. If it bothers you, go to the doctor and talk about options to try and get it regulated. Also, it's not healthy to be underweight, you might need to talk to your doctor about that too.

If you have lost so much weight that you are underweight and loosing your periods this is extremely dangerous and could cause infertility problems in the future. You should really gain weight until you are in a healthy weight and your period will come back.

Are you exercising vigorously and trying to lose weight? This can certainly cause cessation of your menses. Many gymnasts report this occurrence. Have you ceased eating to lose weight? This also can cause the symptom and has a name, anorexia. You need to talk with your friends, family, councelor at school or work and doctor. But if you are eating normally and are still losing weight, go see a doctor and tell her about your symptoms. Check and make sure that there are not other symptoms you haven't mentioned here. You could be eliciting signs of a serious condition. Good luck and get healthy.