Why for more than a year i've had severe mood changes, always sleepy/dizzy/depressed, daily migraines? i'm overweight but i exercise daily for sports.

Life experiences: What if any stressors are going on in your life? Is school going ok? What about your friendships? Are you using any drugs and are they making you feel a certain way? There are so many reasons that could be causing you to feel the way you feel. See your doctor to figure things out

Sleep apnea: Please get a sleep study to rule out sleep apnea. Your BMI(body mass index) may be very high. Exercise does not help relieve sleep apnea. See a sleep specialist. Do not drink too much SODA, CAFFEINE, FAST FOOD OR JUNK FOOD. Read the book by Dr.Fuhrmann-End of Dieting. Do not take too much Ibuprofen either. Good luck.