It is worth going to see your doctor simply in order that you have a record made of your current health problems, in case you should need this for future benefit claims. I have found out the hard way that if your medical notes don't mention something, as far as officialdom is concerned it doesn't exist. You could go to ER and die twice, but without paperwork they'll expect you at work the next day... 
If you're lucky and get a clued-up doctor who does know something about the subject, he will at least be able to rule out a lot of other possible causes for your chronic fatigue. Severe fatigue comes as part of a whole host of disorders - diabetes, which is also characterised by frequent urination - MS, leukaemia, all sorts of things both major and minor. So there are tests that can and should set your mind at ease regarding these, and also others that may at least provide evidence of immunological abnormalities.
If the worst comes to the worst and the doctor does nothing but raise your blood pressure, you can always go down the alternative/nutritional/lifestyle therapy route after seeing him/her. 
But at the least, I'd certainly be thinking about getting tested for diabetes as frequent urination is such a hallmark of that disease.
Whatever you do, please let us know how you get on. Any help you need - we're here ! (When the viruses etc aren't having a good day.... 
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