How can I ask my orthodontist for a palate expander?

The title is basically it, I have a few problems that have been nagging at me for a while but I didn't want to bring them up to my parents since I have already had braces. I notice that while my teeth are closed and like my muscles are relaxed my breathing sounds like I'm snoring, as well as I often bite the sides of my tongue on accident because it spreads into my teeth area because of how narrow my palate is currently. My parents are also kind of dismissive when I brought this up to them, so I am not sure what I would ask my orthodontist anyways.