i've been on bipap at night for almost a year now. i think you will find that feeling will go away as you regain your health and strength. the first few months i had that feeling of weakness in the morning lasting through the afternoon after using my bipap at night. i think it's your body telling you saying, 'HEY, Breathing was just wicked easy, why is it so hard now?!" and you will find that you just need to acclimate to not having air pushed into your airways again. It will hopefully pass!
best of luck! happy new year!
best of luck! happy new year!