breathing stops, memory/ADD problem, chronic fatigue

Hi! I have central sleep apnea/asthma which started it seems 2 years ago with chronic fatigue and O2 levels of about 73% (my FEV1 scores are also 73%). I'm worried my brain cells are dying and I'm having severe chronic fatigue, memory/ADD loss, headaches and sometimes vertigo. I have a neu cyst in my clivus. I've tried bipap with O2 but it doesn't work that well and I'm getting 0% stage 3/4 sleep. What caused my sleep apnea, memory/ADD problem and what can I possibly do? Thanks so much!