Low grade fever and chronic fatigue.

I have been suffering from low grade fever, chronic fatigue, weight-loss, tiredness, low energy, muscle weakness and  unable to focus for the last 5 months. It's been to the point of affecting my day to day activities, being unable to work I had to take time off from work. Even simple tasks exert me a lot, makes me tired and weak. Since then I have taken some lab work hoping for a diagnosis and treatment with no luck. Labs taken so far are: Complete blood panel, chest x-ray, ECG and thyroid . But no findings to get a diagnosis or specialist referral. This is significantly impacting my life in all areas. Need advise on what I can do to get to a diagnosis and treatment for the above. Any help on which specialist to see or what additional tests to take to reach a diagnosis will be greatly appreciated. Thanks!