I’m in burnout again and I feel like a failure

I was neck deep in autistic burnout a year ago. It was years in the making and it finally hit me. I ended up taking two months off of work, had an incredibly long phased return, and reduced my hours to four days per week. In hindsight, I didn’t take enough time off. I guess because I had started looking after myself again (eating regularly, good sleep schedule, interested in exercising etc.), I thought that meant I was ready for work. But any good habits I was able to maintain quickly went out of the window and I went back to barely scraping by.

Now a year later, I’m burnt out again. I’ve been pushing myself to the edge for months just to be able to do my job and now that’s not working. I’m being told off for not completing work on time. All of my energy goes towards trying to work, and then I’m in bed the rest of the time. I’m not eating right, I can’t keep up with chores which is straining relationships with my family, and I’m not seeing friends as much.

To make things worse, my medication has stopped working (antidepressants for PMDD) which means I’m back to having massive mood swings throughout the month. I go from “I feel like a half functioning human being” for a few days to deeply depressed for close to two weeks. I’m also on the waitlist for an ADHD diagnosis but that’s years down the line (yay for NHS waitlists) and private diagnosis isn’t an option because the NHS in my area doesn’t accept shared care.

I know I should go on sick leave again as I’m not fit to work, but my employer has been so accommodating and I’m worried that they’ll get rid of me because I’m wasting their time and money. But I also need a job to be able to afford life and I know other employers aren’t so accommodating. Plus I’m on a trainee scheme so if go on leave again, it’ll delay my qualification even further.

I don’t know what to do. I don’t love my job but I like it enough to not want to lose it. And I feel like I’m an absolute failure because I’m 26 and living at home and can’t cope with having a job. But I can’t keep living like this anymore. Why is so hard to do normal things?

Just hoping someone else has experienced something similar and has some advice.