Don't give up. We all go through a time where we think we're crazy, because Doctors treat us like we are. And that's so fluffing stupid, but there you have it. It doesn't matter if your doctor thinks you're a hypochondriac or not, it matters that you get the medical treatment that you need. If your doctor isn't giving you that, switch to another doctor. You are PAYING THEM, they work for YOU. Doctors have this crazy ability to make us feel bad and like we're wasting their time...when in reality, their job is to work for us.
There are a few things that could be wrong with you. You might have myalgic encephalomyelitis (ME) or Chronic Fatigue Syndrome (CFS). You could also have Lupus, Multiple Connective Tissue Disorder (MCTD), Sarcoidosis, Sjogrens, or who knows what else. But you have symptoms of a lot of these (mainly joint pain and fatigue). When you're dealing with joint pain, a rheumatologist is the specialist you want to see. A rheumy will diagnose any of these things, and most of the time, should understand what is going on and that you're a real person with an Invisible Illness.
So, um, my advice would be to see a rheumatologist. You know that you're sick, and you know that something is wrong. Unfortunately, nobody else can see the sickness...and in fact, you probably look perfectly healthy. It's up to you to be your own advocate, and to get a diagnosis. It sucks, I know, but that's the unfortunate truth.
Right now, I'm going through kind of the same thing you are. I got sick last November, and when it didn't go away for weeks, I knew something was wrong. I was so tired and fatigued all the time... had horrible nausea, and abdominal pain..eventually chest pain, shortness of breath, and then joint pain. I've seen 4 different doctors, had quite a few tests done, and I still don't know what I have. I'm looking at a diagnosis of any of the things I posted above...but because I've been so sick for so long, I've had time to research, and to talk to people, and that's how i know what I do now. I'm still waiting on my rheumatologist appointment, and, like you, there have been many times that i've almost given up on trying to get the help I need. There have been days when I wake up and delude myself into thinking I can just power through it, its not a big deal, its all in my head - like so many Dr's and people have told me. You just have to remember that you ARE sick, that you DO need help, and you deserve it, too.
So don't give up. Try again. Ask to see a rheumatologist, keep fighting for your health, until you get the care you need.
Sorry..that was really long. But i'm hoping for the best for you, and that you figure out what's ailing you soon. It really sucks, I know.
One day at a time, one breath at a time... We can get through this.