I really do hope that your husband does go to see his GP. My GP sent me to the sleep clinic (many years ago now) because I was "sleeping" on and off for about 12 hours every day, the first thing they checked was how much actual sleep I was getting using a souped up oximetre. It showed that I would frequently stop breathing for a few seconds and then start breathing again. I was never consciously aware of it, I never noticed myself gasp, my husband had never noticed it, but there it was, I had sleep apnea. I was lucky in that I never had a problem with the face mask, but I do know that some people take a little while to get used to it.
You can try out different face masks as well. You can get ones that will cover your mouth and your nose, or ones the just cover your nose. If your husband does have sleep apnea, the people at the sleep clinic will show him how to put the mask on, and then check a little while later how well it has worked, and whether it seems to be leaking air at all. Once you have the mask fitting correctly you don't notice the air going into your mouth/nose forcefully, it just feels like normal breathing - well that is until you have been wearing one for a while, and then if you have a power cut, you do notice the lack of the extra pressure. My husband can't actually get to sleep without his now, I can, but you certainly notice the difference, which seems a bit weird to me to notice the lack of something even though you are not aware of it when it is there - however thinking of it scientifically that does make sense, we might not notice the temperatire in our homes if the central heating is on at about18%C, but if it is snowing outside and the central heating stops working, we certainly notice the temperature then!
Yes, my husband now has a CPAP machine too. A few years after I got mine, and my husband had put weight on, he started feeling more tired during the day, so if I when I woke up in the night to use the loo, I would purposely stay awake for a while and listen to him (he had also started snoring more loudly). Whilst listening to him I started to notice a little pause in his snoring, and then a deeper intake of breathe - it never sounded like an actual gasp - so when I told him in the morning he decided to go to see his GP. My husband was absolutely positive that he wouldn't be able to get used to wearing a mask, but he did, very quickly, and as I said earlier, he now can't get to sleep without it. He stopped snoring the very first night he wore the mask, and if I ever hear him start to snore now, I nudge him and tell him his straps (on the mask) need tightening, and all is quiet again. He also stopped feeling the daytime tiredness.
It really is not healthy for him to have sleep apnea, so I do hope your husband puts his concerns aside, and does have an appointment with his GP. By the way, nothing intrusive happened at either my, or my husband's appointments at the sleep clinic. The mask isn't uncomfortable, just a bit strange at first, your husband really has nothing to worry about, but potentially quite a lot to gain. Sorry this is so long, but I wanted to reassure you and your husband that wearing a CPAP machine really is no bother, though if you have senses of humours like ours you might collapse in laughter the first time at how it looks - I am very fond of my trunk (the hose) these days!