I am a teenager but how do i tell the difference between suffering from a mental illness and hormones?

Timing: I'm not sure what you're noticing [could you tell us more?] but think about timing. If you're female, do you feel your symptoms right before your period or during your period? Do you feel better once your period is over? If yes, then it could be related to hormones. The other hormone to check out is thyroid [dry skin, brittle hair, tired, feeling cold, weight gain too?] a blood test checks thyroid.

Mental illness: If you find yourself questioning your sanity then it is time your spoke with your parents about seeing your doctor for an examination. The changing of hormones in teenagers can cause some emotional turmoil, however feelings that you might be mentally ill needs some help with sorting out your problems. Be sure you are liviing a healthy lifestyle and are not taking any drugs or alcohol.