more tired than before CPAP

I was always known as the lady with so much energy. Went to bed at midnight or later, slept good til 8am. Maybe got up 2 times to go to the bathroom. Back to sleep, no problem. I am now 79. Have lung problems, high blood pressure and arythemia for which I take toprol. They wanted to do a sleep study. 52 episodes on my back and 9 on my side, mild sleep apena they said. I usually sleep on my side but in the sleep study with all those wires I was on my back and only slept 2 hours restless. Terrible night . Went home and slept good for 6 hours. Have the full face mask. Use it for 4-5 hours. Sleep very restless. Take it off and sleep sound for the next 4 hours. Now I am tired all the time. My life has changed with no energy. I thought it was old age. I have used the CPAC for a month and about to go back to my normal good sleep.