Struggling with Work and Mental Health

Having a really hard time with work. It's my first job other than self employed pet/house/babysitting. I got hired less than a month ago and I just feel so incredibly burnt out, depressed, anxious, and in pain all the time. All of my time is going to work and recovering from work. I tried to spend time with some friends but it was too much for me now. On top of that I am a monitor at a homeless shelter and it is occasionally very triggering to my PTSD, in which case I tend to shut down and dissociate which means I don't end up doing the things I'm supposed to do. (Something was going on and I was supposed to call my supervisor or security but I shut down and went non verbal and couldn't do either.) So far I haven't gotten in trouble about it but my coworkers have seemed very annoyed with me and I don't know if they actually are or if that's just me and my anxiety thinking that. I'm thinking about maybe asking to be part time instead of full time but I don't know if that's an option or how to script for a conversation about it with my boss or supervisor. I'm honestly so tempted to quit and have been every single day I'm here. I've been living with a friend for almost a year and she says she's more than happy to share her space with me regardless of my ability to contribute financially but I just feel so bad being so dependent on people. I feel like eventually people are going to be tired of helping me and I'll be on the other side here, homeless. (I know this is mostly my brain/anxiety catastrophizing, but it's also partly based in past experiences.) ((trigger warning: self injury, suicide)) I've been so stressed, and it's similar to how I felt in highschool, where I ended up having to drop out after being so mentally drained and my mental health being so bad that I was in and out of psychiatric hospitals for self injury and suicide. And I feel like I made so much progress since dropping out and it's all just rapidly unraveling and at this point I'm very very scared that it's going to get that bad again and it already feels very close. I went form going months at a time without suicidal thoughts to having them almost every day this week and last and being so tempted to self harm to release the stress. I'm going to talk to my therapist about it in 2 weeks (had to reschedule because of work) I just feel so defeated, any advice at all would be very much appreciated but I doubt anyone read this far.