Anyone else feel like you're drowning every minute of every single day? How do you keep your head above water being a TRULY alone parent with 0 support with a child on the spectrum?

I'm sorry this might be a little long. So sick of pretending like everything is ok, and we're going strong! I feel selfish to be saying this but I feel like the last 4 years I've had 0 quality of life and I'm heading into a quality of life deficit. I'm scared I'm losing my will to carry on. Just when I think it will get better, it just gets more difficult. I don't think some people/parents realize how alienating fully parenting a child on the spectrum by yourself can be. I don't know how or where to find support or other parents that can relate to my situation(I've looked locally) so here I am. Desperate, exhausted, crying, sad and hurting not knowing where else to turn.

45 now, empty nester of 2 adult kids. At 42, I discovered I was 6 months pregnant. I was utterly devestated. Precautions were taken (2 different ones) and I still got pregnant, WTF. His father is someone I dated briefly and cut ties with due to many red flags early on. He has 0 involvement financially or otherwise.

Not only did I get pregnant, I was fit and my body did not share it's secret until it was much too late to do anything about it.
I shut down and buried myself in work even more. I worked and went on maternity leave 9 days before my water broke.

I realize that already being an introverted workaholic hermit, I wasn't in a great scenario to begin with. My parents are both passed, I have no family or friends that live close. We have absolutely no one and no support. I have 0 breaks, 0 help and I don't know how much longer I can go on this way.

My surprise is now almost 4. His case is "severe?". I knew very early on something was different with him. I kept on our GP about my concerns and my LO was diagnosed on the spectrum at 2. I was so hopeful, thinking ok, we have a diagnosis now we know what we're working with. I have him enrolled in a special preschool which he goes 4 times a week from 8-1 and he also has services with him twice a week until he goes to school. The older he gets, the less helpful/cooperative he is.

This winter has been the worse. At almost 4, he's 3 1/2 feet tall and weighs 48 lbs. I'm 5'2 and he's already almost a third of my weight. He does what I call the "ragdoll" for any activity that involves getting dressed. I don't even know how to explain this but he makes his feet "limp". I have to bend his foot and hold it with one hand/arm so I can put his boots on. By the time I have that child dressed in the morning I am exhausted, frustrated and on the verge of tears.
He doesn't help or cooperate with any daily task. If I try to make him walk or stand up, he makes himself "crumple" to the floor and just stays limp. He gets incredible enjoyment from this and enjoys every moment of it giggling and smiling. It's so incredibly exhausting, not only physically but mentally.
How can I live if this is the battle I am already facing and he's not even 4. At this rate, I feel like I am fighting a losing battle. That is only one example, there are so many other hurdles on a daily basis.
How can I return to work and try to have a semblance of a normal life if I can barely get the child put of the house without using every ounce of energy I have?
I can't be the only one struggling on silence.