I have CFS and it usually starts with what seems like a viral infection that just never goes away. Poor sleep is also involved. That doesn't mean you have it, but it is important to see a doctor. It is often a diagnosis of exclusion, after many tests come back normal.
If the doctor finds nothing wrong with you, be careful that they don't convince you that you are just depressed. That is what they usually do if all the tests are normal. Anti-depressants can just complicate things. If you continue to have the fatique and sleep problems, see a doctor that specializes in CFS. The earlier you receive treatment, the better chances you have for a recovery.
Hope it is something simple that they can help you with. Good luck! Sincerely, Choosing Life