My partner and I both have ADHD and each spent some of our younger years floundering - poor grades, dropping out of school, fired from jobs, underemployed/unemployed.

He currently sees an occupational therapist for organizational strategies like bullet journaling and it helps a lot. I think you’re in Ontario (hello neighbour!) so it should be covered by OHIP. I’d see a doc to get some meds too if needed. Undiagnosed ADHD is a bastard and it would help you a lot to get it sorted first, as a strong foundation, if that’s what’s been causing problems.

Job-wise, I’d suggest something where you’re not at a desk all day. My partner is a media technician (film, photography, digital) and I am an event producer. We both found jobs that play to our ADHD strengths. Lots of suggestions here for skilled trades which might be good! If you told me 10 years ago that I would be happy/fulfilled/well payed in a job, I never would have believed you. I’m in my forties now and things are great.

Today is your day to change things. Make small steps. Focus on feeding your body in healthy ways: good food, sleep, regular exercise. You need that stuff in order to really do well at a job.