I agree with EverHopeful that you want to rule out pulmonary embolisms. The symptoms with that, from what I've heard, can feel quite similar to the weakness and breathlessness of ME. My father has had pulmonary embolisms and has to take warforin. He had extreme out of breathlessness and weakness and went to the hospital, where he found out it was an embolism. So he understands, unfortunately, what some of the very worst ME symptoms feel like, though he doesn't have ME.
I really hope you don't have pulmonary embolisms. For my breathlessness with ME, which has never been as severe as what you've described, I've used a home oxygen concentrator with some success. I got one second hand online (craigslist) but if you could find a doctor who would let you try that might be an option. I've started the B12 protocol that is talked about on this forum and my breathlessness has gotten better but is still sometimes there and worse with exertion.
I really hope you can find a way to get your breath properly as this is such a disturbing symptom. Take care.