I'm always tired, have a low appetite, and am constipated. i'm also vegan and eat a ton of veggies and vitamin supplement. what could be the problem?

Tired : This could be related to low thyroid as that could cause all of those symptoms. The other thing to consider is are you getting enough protein in your diet? This is something to be evaluated by your PCP.

Daily bowel movement: Constipation is often the reason for poor appetite. The GI tract is a long tube ~30 feet long. Imagine the kitchen drain that is clogged at the lower end and we keep adding stuff on the top. Correct constipation with increased water intake and goods oils for lubrication, and high quality probiotics. Fatigue is commonly due to hormonal imbalance especially adrenals. Find a holistic doctor.