Anyone quit CPAP because they felt worse?

[Nightynite]

Report back after you see your Dr. about your blood work. It will be interesting to see if it’s your blood sugar is a little high.

[Sleepster]

So I had not been tallying my calories before conducting my "experiment", but I have a pretty good feel for what I was taking in (about 2000-2200 calories per day).

If you could rely on a "pretty good feel" there'd be no need for you to keep your spreadsheet.

I agree that 2.5 pounds is not a huge amount and under ordinary circumstances it could be due to fluctuations in water retention/clothing/hormones/etc., but over a period of three weeks in which I felt like I was starving myself, to me it was signficant and demoralizing, especially when added on to the 10+ pounds I have gained since April.  And for me, it was more like a 2% increase in my total weight.

Demoralizing hits the nail on the head. We likely suffered with untreated sleep apnea for many years before we were diagnosed. Our bodies had all that time and experience to adapt to that way of sleeping. It will take some time to adapt to the new circumstances. Don't be so hard on yourself.

I gained weight when I started CPAP therapy. I thought that the CPAP machine is the cure for all my troubles and let down my guard against eating too much.

For most folk, CPAP therapy is a weight-neutral undertaking, but there are some studies showing that a very small subset of people DO gain a modest amount of weight.  The conclusion drawn in some of these is that multiple apnea events each night raise the individual's Basal Metabolic Rate and once the apneas are resolved, the BMR drops and weight creeps up. 

That could be what happened to me, but you have not had any significant change in your weight. It could be that you are more conscientious about your diet than me so haven't experienced the weight gain that I did.

But it doesn't matter! All of this is transient. It's part of the adaptation process. Just maintain your exercise and diet regime and CPAP use and it will all resolve itself.