It might be best to have a sleep test before you self diagnose. I have improved in health and sleep since I was diagnosed with apnea. Now that I have a CPAP machine, I have never felt better.
I have read that inaccurate doses of melatonin can raise blood pressure,cause fatigue, depression and affects fertility. Naturally you should check that you don't have heart problems or hypertension before you take any hormones or drugs because you don't want complications of stroke etc.