How do you handle your meltdown/shutdown? (long post) (I need tips, advices or your experience)

About me: I didn't get my diagnosis yet (yes I know that self-diagnosing isn't fine, but I really can't visit a specialist right now) but keep experiencing signs that I have it. I (18M) used to be worn out after any socialising for my very childhood but am sure that nobody gave attention to it. I skipped most days of school because of this. I believed I had ways or knowledge how to handle my state after socialising but this year it increased (probably because I got into college).

Situation: Past two weeks I couldn't get any rest because my family members were at home and also I had to get my cat to vet. This made me socialise 3x or 5x more than usual and after that I felt so worn out that couldn't stop cry and shake. Last week, I tried to get some rest (sleep, do things that I enjoy, reduce chatting and socialising, didn't open a single social app) but it didn't help much. On weekends I did groceries and to the evening my body snapped. I had my temperature raise and fall despite cold wind and rain, wanted to cry all the time and sleep but couldn't. I still shake after a full day and feel overwhelmed with everything way too much. I know that self-diagnosing is bad but I noticed that strategies that people with autism use to live, handle stress and procrastination help me. So if you ever experienced that or something familiar I'm really open to advices/individual experience.

(sorry if the text has grammatical mistakes or looks weird, english is my second language)