Do keep trying with the Doc, but also don't discount the fact that you may be depressed. The first thing that I generally notice when I am falling into depression is the fact that I am always tired, and regularly sleep for England - my colleagues also notice that I stop being sociable.
My GP Nurse took blood when I said I was feeling exhausted and tired all the time, fortunately they came back clear, but that did mean the Doc upped my antidepressants which sorted the problem slightly...

Good luck with finding a solution - I generally find that fresh air being outdoors - even if it is only watching the world go by, will assist ...