I have Selective Mutism and crippling social anxiety, should i go on a school trip in a month?

Context: I’m in my last year of high school with basically no friends and we have a school trip slightly more than a month away and we will be staying for a few days. Throughout my years, many classmates have tried interacting with me but 95% of the time, i get really anxious, uncontrollably become mute, and end up ignoring them, even though I really want to talk and be their friend so now i have basically ruined all my chances. I found that I have basically all the signs of Selective Mutism, and I suspect I could potentially have autism/adhd as well.

My parents are going to find me a therapist and/or a psychiatrist soon so that I can get properly diagnosed and fixed, but im not sure that i can quickly get better in a month. Even if I do manage to get better, all the people I ignored will still probably have a negative perception of me (which is understandable) and i dont want to bother or annoy them by going.

If i choose not to go, Im instead just spending one day at the beach with the third years. I do have one “friend” in third year (met before hs), but they think i should go and not waste my high school (which i kinda did already) and i noticed he sometimes gets annoyed/frustrated with me in large doses (since im still slightly socially anxious and mute around them for some reason, though not as much, even though we have literally known each other for years). My parents want me to go on the trip too but they dont know that i have no friends and ruined my social life (i was vague when i asked them to see a professional for selective mutism/my other problems). A part of me kinda wants to go but my high school years have already been pretty traumatizing so far and i know that i will probably just be mute the whole time (unless therapy fixes me quickly) and it will be a waste my parents money. I also dont really want to go to the beach since im most likely also gonna sit there mute since my “friend” will probably try to make friends of their own and i dont want to feel like im stopping him from doing so (especially if im introduced and i go mute and they think i have a problem with him being friends with them).

I know its my last year of high school and i shouldnt be overthinking something like this but i cant help myself (i be overthink everything, even whether i should post this). Sorry for the long post and if it feels like im venting (haha amogus) but i really just dont know what to do and i have to decide by tomorrow (and my best solution apparently is to ask random strangers on the internet who dont know me and prob wont read this anyway). How long does it usually take for therapy with a decent therapist to start “working” and how long does it usually take to set up the first meeting? I might lean towards going if i get better quickly but i read that selective mutism can take a while to fix so irdk.