Can oxygen do harm? i use cpap with o2 kept feeling worse. i stopped o2 now feel much better with more energy. stats were in 80's.

Usually not: You did not specify when were your o2 sats in 80s - awake or during sleep with cpap? You may have co2 retention which can be masked with use of o2. Once you stopped o2, it increased your respiratory drive allowing excess co2 to be flushed out. Please see a sleep specialist ; get a CPAP titration study done to accurately assess your pressure settings. You may do better with bipap instead of cpap.