Have your thyroid checked. Yes, it involves a blood test. Blood test are nothing, think of it this way; small children who are in bad health get them all the time.
When I was young my concerns were ignored, the doctors would always say I was too young for anything. At 28 it got worse and by 30 I was diagnosed with a goiter (I recently had surgery). Goiters are not common, but regular thyroid conditions are (I know a few people w/hyper or hypo thyroid).
Depression, anemia can also makes you feel tired.
P.S. Because I had a goiter & nodules, I would get needle biopsies (more than one at a time) on my neck, several times a year. Believe me, a blood test from the arm is nothing.