I am afraid I have something more serious than needing a cpap adjustment.
But you will never know that if you don't talk to your doctor!
My mother was diagnosed with OSA and Narcolepsy at the same time, used a CPAP for years. Shortly after we moved to Arkansas, she stopped using it because she couldn't sleep with it on. It took a while, but I finally convinced her to talk to the doctor, who had her retested. Turned out she didn't need the CPAP at all, anymore (she'd lost a little over 20 lbs). Also turned out she was supposed to get retested on a regular basis, but no one ever mentioned that to her when she originally got the machine. And the original test was done because she found herself falling asleep at the wheel, though thankfully it only happened at red lights.
So, I don't know how long it's been since you started using the CPAP, but if it isn't working you definitely need to be retested, and possibly have it adjusted. When you talk to your doctor, that's likely to be the very first thing s/he wants to try and see how it works out before they do any further testing.
And, yes, it is perfectly possible to fall asleep standing up, and even to do so without falling over.
And, my own personal advice, since you know that if you're driving for longer than half an hour you're going to "blank out" and lose control of your vehicle, STOP! Pull over (somewhere safe), get out and walk around a bit. It doesn't have to be long, just long enough to restore your alertness. And do so every half hour. That may mean you have to allow extra time when you're on a schedule, and yes, it's a pain in the butt, but it's better than wrecking your car and possibly hurting--or even killing--yourself or anyone else!
When you go to talk to your doctor, it wouldn't hurt to print out your posts here and take them with you, so you don't miss anything. Your doctor isn't likely to file with the DMV (or whatever the local equivalent is) to have your license taken away, as long as you can tell him/her that you're taking steps to correct the problem (see the paragraph above)--and doing the testing and looking for an answer and appropriate treatment are an important part of that. But, if the police see you swerving off the road and pull you over, you can get a DUI for driving while you're tired/sleepy/sleep deprived. I've more than once had to stop, get out and walk around and had a police officer pull up behind me to ask what I was doing and if I needed help. When I answered, honestly, that I had pulled over because I was tired and having trouble staying awake and I was trying to wake myself up enough to get where I was going, they have invariably thanked me for doing so and told me they'd appreciate it if I continued doing so and they wished others would as well. It was one of them who confirmed for me that if they have to pull you over because you're falling asleep while you're driving, you can get ticketed for DUI.