I'm so scared I'm third wheeling

I’m nervous about an upcoming gathering. I feel like I won’t be welcomed or only invited for the sake of the host being nice. I am afraid of what I will say or do, that others will pick up on my non verbal behaviors like I do with theirs (i.e. a shoulder shift, eye roll, texting each other while I’m right there etc.) and I’m afraid that I will ruin the vibes of the gathering by becoming paranoid. I don’t want my thoughts to spiral so bad that I need to leave and my fiancé is out of town so it’s not like I can escape. I don’t want to be there the whole time but also don’t want to seem rude by leaving early and keep thinking that if I leave early will be a topic of conversation for others there. It makes me want to curl up and hide in the house all weekend and I haven’t been able to stop thinking about it for over a week now.

i'm chatting with this person on discord. i don't know why i think that way, but i started questioning whether they secretly hate me or will judge me in some way. i always expect people to leave me and i'll be all alone. it's scary them not responding to my messages sometimes also fuels that fear. i know they're busy or get distracted sometimes, which isn't their fault at all, but my brain won't stop making worse case scenario and therefore i'm constantly checking when they'll reply to me. they have proved multiple times to me that they're a good person, that they like me and that i have nothing to worry about, yet i can't stop ruminating on the hypotheticals i made before starting to talk to them on a more personal level. i feel like i'm going crazy. my only salvation is random distractions and heart meds.

the past month ive been ruminating about a time last year where i hurt a friend by unintentionally bringing up a traumatic memory when i was really drunk, enough that i didnt remember it, so i went 6 months without apologizing until i was worried when they werent talking to me anymore. so they told me when i finally tried to talk to them. i apologized and they told me we were ok now, and still want me in their life, but now they stopped talking to me again and its been 3 weeks, and im terrified that i did something again, especially since they stopped talking to me when i made a mistake before, and wont tell me outright. the event triggered horrible horrible guilt over what i did, mostly guilt About the guilt i was feeling, because its not a normal amount of guilt for a regular person, and eventually my compulsions for confessing and ruminating reached a high point. and when they stopped talking to me again they got even worse . they are aware i suffer from ocd and anxiety to an extent (we've been friends since we were teenagers) so its hard for me to believe they wouldn't do this unless i did something wrong again, especially due to the events of my past mistake. lately ive been wondering, 'have they found out my abnormal reaction to what happened ?' 'did a friend who knows about it tell them?' ive been avoiding asking them if i did something wrong again, because i dont want to make it a habit since i can fall very deeply into that hole of asking for reassurance and i feel even regular reassurance, without the ocd, im the last person who deserves that right now. im scared they somehow found out about my compulsions (which isnt entirely irrational) and i feel the need to apologize to them again. ive been having panic attacks about this. i feel like no matter what i do i cant fix our friendship, and its going to end badly. i feel like a terrible friend, and im too mentally ill to have friendships. i don't know what to do.