I am currently where you are. I cannot be standing for too long or else i have a hard time breathing when i do sit. Also, palpitations begin if i stand, walk, talk, or even be on computer for too long. I was having some joint pain the other day as well. I have been this way for the past two weeks. I don't feel tired and wired strangley enough though like i usually felt before. According to lam's article it is possible that i may be in stage 3D, because of your anxiety and tired and wired feeling i would say you are still in stage 3C but bordering 3D, just my guess. I think you need to rest, and also the most important thing right now is that you find out how to calm down. I've been in stage 3 for about 4 months now, but it has never gotten as bad as now, nevertheless i still believe we can get out of this. Many others have. Labored breathing is probably the most disturbing symptom for me. Keep in touch with me, since you sound like you're in a similar stage as i am, except for the anxiety - it comes only if i over-exert myself (like walking to far, or simply stepping outside for about a minute or two).
How long have you been feeling like this?