First of all, believe it or not, congratulations! If you were able to fall asleep with no problem and only had to tweak humidifier settings to get something that works for you on your first night, you are significantly ahead of the curve compared to most people, myself included.
I would recommend that you get the latest SleepyHead software
, install it on a Windows PC, and have a look at the data on your SD card to see how well you actually slept. You'll need an SD card reader attached to your PC. Any one that reads SD cards will do; if you don't already have one, you should be able to pick one up at your local computer store for anywhere from $5 to $40, depending on how many other card types it also reads.
As to your aches and pains, is it possible that, for the first time in a long time, you slept really soundly, relaxed more than you normally do at night, and therefore are finding out that your sleep position and/or bed firmness is not to your ideal? A lot of people (again. myself included) find that they get back pain between the shoulder blades shortly into their CPAP experience. My guess is that it has something to do with what might be a slightly different head position because of your mask. Most people report that it goes away after a while. As I type this, I still feel a bit of a twinge, but I seem to have it under control by taking a couple of Ibuprofen before bed.
The other possibility is that, like me, your diaphragm (which is a muscle) was not used to the extra work of the CPAP pressure, and ached in the morning like any other muscle getting a significant workout. If this is happening, it should go away after a week or two as your diaphragm gains strength.
Try to not get discouraged and give it some more time.