Establishing routine while in grad school (or any flexible schedule)

I'm diagnosed and on medication, but I've found my executive function has absolutely plummeted since I started grad school in the fall. I'm only in class two days a week, so the rest of my schedule is totally flexible. I spend most of the week at home procrastinating literally everything - school work, exercise, cleaning, errands, and even things I WANT to do like hobbies and socializing. I know that I need to establish a consistent routine, exercise, eat healthy, etc, but I just. can't. do it. Every day I end up telling myself I'll start tomorrow instead. I made a habit tracker, but like every other form of to-do list or calendar I've tried before, I used it for a couple of days and then completely forgot it existed.

I think part of it is decision paralysis because I don't have an immovable obligation most days of the week to build a routine around (like when I was working a 9-5 job). For example, I know I want to work out most days, but what time? I'm not getting up at 7 am to work out when I don't have to. Late morning would be ideal energy-wise, but then by the time I get home, shower, dry my hair, and get dressed again, transitioning into another activity or task seems overwhelming.

I could elaborate about all the other reasons I think this is so challenging for me, like lack of body doubling since I'm single and spend most of the day alone, lack of urgency, time blindness, etc, but thinking through all of those reasons hasn't gotten me any closer to figuring out a solution. On top of all of that, even though I have a social life, I feel pretty isolated. I have close friends and family around but most of them are settled in serious relationships and careers, and most of my classmates are in a different life stage (I'm in my mid-30s and most of them are in their mid-20s). I feel like I'm missing an anchor and I'm just floating around.

I'd love to hear from anyone who has been through a similar situation, whether you have advice or just to commiserate!