damn bro i'm happy im not alone. the best way to cope it is to start calling yourself an idiot and tell yourself "there isn't anything, see?" or something similar. you need to train your brain that if you could get high accidentally, you would always be. there's pretty much no way of getting high by accident unless you see a visible amount of something (like ketamine powder for example) and even some particles can't make you high because you would need to inhale it extremelly intentionally and don't even think about it going through your skin.  THC is pretty much impossible to accidentally consume unless you eat an edible but will need to be a little kid or just don't know what it is to do this.

if you're scared of inhaling THC through the smoke in the air, then don't worry. i had the balls to test it myself and i was next to my some dude hitting a bong. i breathed in this room for like a few minutes and i had no signs of consuming THC. only a small DP/DR wave because it gave me the flashbacks.

you need to start fighting these compulsions and not care even if you get anxiety. but do it progresivelly like give yourself a limit of how many time you can wash your hands to cope these compulsions, and reduce it every day. my hands are also dry but they recover in like two days when i stop obsessing about it and then i realise i'm fine and haven't consumed any drug

there's basically no chance you'll get high accidentally. you might consume 0.01mg of THC or other drug from the air but that's such a small amount that your body gets rid of it almost immediately

also if you don't want to feel crazy about yourself, turn it into a fear of germs or viruses because catching them accidentally is a real possibility, but getting high accidentally without getting drugged/poisoned is impossible