And welcome to the forum!
When you wake to find the mask beside you, is it because you it came off in your sleep and you don't remember it happening? For many people, myself included, in the beginning I would take the mask off in my sleep without remembering doing so. It's the brain taking off that unfamiliar thing on your head. Eventually the brain gets used to it, but it's important to try and go to sleep with it every night if possible, try not to skip nights. Some people here on the forum might have some tips about keeping it on, ways that make it harder for you to take it off in your sleep.
I'm a little doubtful your prescribed cpap pressure is 5. It could be higher. The cpap machines come with a ramp, which the supplier often sets when you get the machine. It starts off at a low pressure, usually 5, and over a set time period, like 10 or 15 minutes or more (whatever it's set to), the pressure rises slowly to your prescribed pressure. The ramp is designed mostly for newbies, to help you fall asleep with a lower pressure so your body gets used to it. But it's not for everyone. Some people feel they're not getting enough air, until it rises to the appropriate pressure.
Be sure to have followup appointments. If you still have problems with the breathing of it, contact the doctor or your equipment provider and set up an appointment. It could be just getting used to it. Some people can only sleep with the mask a few hours at first but that gradually increases. But if you continue to have breathing problems, it could be something else, especially if you have trouble breathing against the exhale. You might need a different type of cpap machine or a change in the settings. Or you might need a different type of mask for your type of breathing.