Sleep Apnea Support Group
Sleep apnea is a common sleep disorder characterized by brief interruptions of breathing during sleep. People with sleep apnea partially awaken as they struggle to breathe, but in the morning they may not be aware of sleep disturbances.

You wrote that you are physically sick all the time and in a lot of pain. You need to get these two addressed also. If a person has chronic severe pain, that person is very likely not going to get the recommended amount of good sleep (6-8 hours typical for an adult). SA may cause the sickness, but that would not be my first guess. As for pain, who knows based on what you have posted.
My non-medical opinion is to get back on your CPAP tonight, and get a new sleep study to make sure that your pressure setting is correct (likely too low now IMO). A better type of machine for SA is an APAP. This type of machine can find the pressure needed to help fine tune results plus allow for easy adjustment by the user. If a new sleep study is not financially possible, then I would first recommend restarting your CPAP, and then start looking for a new, or used, APAP machine. An APAP machine if you have to pay 100% of the costs can be brought for $600-$800 at online retailers. However you do it, get back on CPAP now.
As for the items; sickness and pain. Not sleeping can cause both unless you know of something specific not mentioned (for example, pain caused by a bad back). If your SA is not causing either of these two problems at least you can eliminate one possible cause.
Good luck!!