I agree with Juls that it´s hard to suggest why you feel so tired. I mentioned in an earlier post to you that my low quality living drained me, but that was perhaps an extreme exemple, as I lived on the streets.
I think in some cases, sleep is an escape. Once, after something bad happened in my life, I slept one winter away. The fatigue overtook me and I slept and slept. I was depressed and denying life. I felt sleep was a drug and in a way it was. I thought I would never get out of it until I went away from Paris to another country to work on a project. That jolted me out of it and I started slowly to come back.
I urge you to get help and support. There are ways to get medical attention on a low income as I believe Phoenix suggested to you. Unfortunately, I´m in Paris and we have a different health-care system.
Good luck.