The only way I could describe my feeeling of "fatigue" to the doctor was...It's as if I have taken a sedative and my brain slowly becomes sedated. If I do not lay down, I feel like I will collaspe. Not faint or pass out, but my body WILL go down. I also cannot process words if someone is talking to me.
From what you describe there with all that.. I personally think you extremely likely do have a orthostatic intollerance issue (dysautonomia) going on and should be tilt table tested to find out which.
Thou I used to get dizzy with the postural orthostatic tachycardia syndrome (POTS) .. I dont get the dizziness with it as much now and often it now just manifests as a slowly worsening brain state along with that feeling that if you dont lay down you will collapse (desperate need to lay down). It is likely you actually may at some point find that a full collapse or even unconsciousness may occur if you were actually forced to stay upright too long.
When blood isnt getting the ones brain well due to an orthostatic intollerence issue.. ones brain struggles to function too and this can make talking or thinking/understanding hard. It leaves me at times unable to understand language or talk.
If Im correct that you have something like POTS, you will likely have to find a different specialist to a ME/CFS one for this as most (not all) ME/CFS specialists dont have a clue when it comes to POTS.
Your current illness seeing you are having trouble getting a good diagnoses from your doctors, it may turn out to be not ME/CFS but just something like POTS which can cause many ME/CFS symptoms and hence can be confused with ME/CFS.
You may be able to work out whether you only have POTS (or another OI issue) causing your symptoms or whether you have both these things (having both are very common in ME/CFS people), by the posts and getting advice on this forum and IF it is POTS, that is testable even at home so at least you should be able to find out for yourself and then know what info to be getting across to your docs (doctors dont have a clue when it comes to less common conditions). Once you've sorted that out.. you will know more what kind of specilaist to be trying to see first... POTS/OI specialist or a ME/CFS specialist or if you need to be seeing both of these.
I suggest for you to read up on POTS but understand it manifests differently for different people. One thing all POTS people tend to have is an urgent need to lay down at times along with worsening symptoms when upright or on ones feet. (the POTS heart stuff you may not notice going on at all with it unless you are actually taking your pulse or better still using a monitor and POTS testing correctly. POTS is diagnosed by how your heart responds from laying to standing. It isnt a heart issue as such as ones with it do have healthy hearts thou but rather an autonomic disorder.. dysautonomia.).
http://www.dinet.org/pots_an_overview.htm (check out this link and site).
I strongly suggest to avoid getting labeled with "CFS" IF all your symptoms can be explained by POTS (as a CFS diagnoses could affect the treatment you get from many doctors and having another diagnoses which explains all ones symptoms is meant to rule out CFS). So if it does turn out you have POTS (when you self monitor) you may want to just focus on that.
Things like sore throats, swollen glands, immune issues as part of your symptoms thou would point more to you also probably having ME/CFS on top of having an OI issue as they arent symptoms those who just have POTS alone get