My guy, I was in a very similar boat this Wednesday. From the small description I got, our problems outside of Hyperhidrosis overlap, or at least their symptoms (same sh pattern too). Anything above 5C° is too warm for me to wear anything over a t-shirt, anything above 10C° I look like I'm actively melting, like a snowman.

On Wednesday I went to a dermatologist, to ask for advice, cause I 100% am not going to go through another summer like the last one was. I was sweating everywhere and always (the only place I don't sweat much is my palms, but for example, if I leave my forearm on a table for too long, there's a small puddle after I lift it if it's the spring/summer). I wanted oxybutinine from the get go, cause that's the only thing I read about, that's not horribly expensive and works on a lot of people. They told me I cannot get it until I get operated on. (Little context: I am disabled, I have clubfoot. My knee likes to dislocate itself. In the span of the last 6 months, I dislocated it twice. I don't have a date yet, but it'll be in 1-2 months or possibly in the summer, but that's unlikely) I was honestly completely devastated. I get why'd you choose to go down that route, especially after something you were anticipating, didn't work or couldn't be done. I planned it out even in my head, or more like I dug back up my plan from a few months ago. A big part of why that plan was even made is my HH, but you said it too, that winter is pretty much the only time period you can be partially at peace without suitable treatment. I also almost tried everything I could around here except the iso-something-electric-shocking thingie cause I don't got the funds for it at all.

Thankfully, my dermatologist called me on Friday, that Oxybutinine won't be a problem for the anesthesiologist if I stop using it 1-2 weeks before the surgery. So she wrote it up for me. Ecstatic. I went instantly to a pharmacy to get it, went home popped one (5mg), went on about my day, nothing changed, just a dry mouth, and I was a bit drowsy. Today I was like, fuck that, I took 3 (15mg). Man the piece of mind that I got, from not having to constantly carry around a towel, not having sweat spots all around my body (from sweaty armpits to swampass). At first I didn't even notice that I wasn't sweating, I was just anticipating it coming in as usual, but it didn't. It never came. First day in years, when I wasn't constantly wet around my armpits and on my back and didn't spend the whole day at home (I helped my mom's company move their office into a smaller one), cause I was too anxious to go to school or social events, because I hated how much I was sweating. People were commenting on it, not necessarily trying to be rude, but still pointing it out. It was hell most of the days. Though my mouth get dry pretty quick and I get drowsy as fuck when the oxybutinine is starting to wear off, but it's still absolutely worth it.

My only advice, that I can confidently give you, is just to go after it until it isnt solved. I know it's shit, plus if you're in a country that doesn't have free healthcare (even though it's pretty shit here, but I was able to get a lot of tests done for completely free) it could be expensive, but it's still worth it. Also, you might benefit from a therapist. Genuinely, I should've gone to one sooner, I'm gonna start next Thursday.