Any advice for binding while in insane heat?

I live in a very hot state, around 100 Fahrenheit (38 Celsius) daily. I’ve been binding for over 4 years now and as of the past month or two I’ve been having a really hard time breathing whenever I’m outside in the heat with a binder on. I haven’t had this issue before, but now I can barely be outside for 10 minutes without not being able to take in a deep breath and just overall feeling crazy shortness of breath. I don’t have this issue when I’m indoors with my binder or when I have it off completely. It’s only when I’m in direct sunlight and heat.

Because of my past schedule, I’ve had to wear my binder for about 12 hours a day 6 days a week, but all of my day was spent indoors.
(My binder does fit me properly and it’s not small on me)

I’m starting college soon and I’d have a 15 minute walk outside and I’m kinda worried that I won’t be able to breathe. (I’d also be wearing it for less time now, about 5 to 6 hours a day) I’m worried that my past binding is catching up to me and I can’t fix this.

I’m also not out to my parents so I’m not able to ask them for help or to see a specialist.

Does anyone have any advice on what I can do or why I’m even feeling like this?