fairly sudden onset-severe difficulty breathing, muscle weakness-can't climb stairs, can't lift above chest level, recover with rest; over next two months, inc. in difficulty, balance is off, all tasks becoming more difficult, just holding my arms out for 15-20 seconds feels like I ran a marathon, breathing better with steroid inhaler, no difference with albuterol, face begins to hurt with chewing, smiling, increase odd feeling when swallowing, dev. odd breathing pattern when having long conversation, voice becomes hoarse after speaking for a few minutes straight. Walking/standing still becoming difficult. No general fatigue, no numbness/tingling/no headache-dizziness. Basic labs neg. ACE receptor blocking/binding negative/Rheumotologic tests neg/Lyme neg/slightly elevated d-dimer; neg MRI neg Chest CT neg chest xray; intermittent back pain (like someone shoving fist through spine-neg pulmonary embolism), this is newest sx? What else should I be paying attention to? Does it fit anything else at all?