I've had similar problems to this, although my back pain is a bit higher, and creeps into my neck and jaw. I think I've lessened the pain a lot, but it is always somewhat there. Here's what I've learned, tried, and done. Just going to say though this may not work for you, since it might be completely different.

For me, it is my right side, not my left (and I'm left handed). But sometimes I will get pain on the other side as well. I think it's a combination of RSI as well as getting rear-ended by a car. I've never gotten surgery, but I have tried almost everything.

I started with going to the doctor, getting opiates and muscle relaxants. The opiates helped a bit, but the brain fog made it harder to do my job. The relaxants didn't help much. In the end, my back was so tight, it was like a rock, which then became the source of the pain as I couldn't get it to relax, and the stress would build.

Then I started getting professional massages. If you haven't tried this yet, let me assure you, they are completely worth it. Professional massage therapists are amazing, and they really know the body, and have probably dealt with dozens of people with pain like yours. They are a great resource and as good as a doctor IMHO for showing you exercises and stretches, since they will feel your body and know exactly what is tight and/or seemingly wrong. Doctors never seem to get to that level of detail, they are just too busy and don't have the time, nor are they as touchy-feely in general.

Massage, pain killers (especially ibuprofen and other things to reduce inflammation) and heat (hot baths, jacuzzis, spas) really can help to relieve symptoms. Even a few days break from the pain is good. I would also suggest medical cannabis, just because the chronic pain is bad, which makes stress, and that only makes the pain worse. I've had off and on luck with chiropractors, although I don't think it was as helpful as massage, but it is generally cheaper (and covered by health insurance). Also, check how you sleep! I noticed a lot of improvement once I got a new mattress, and I realized sometimes sleeping without a pillow and having my neck flat was better than a pillow.

Once you manage the symptoms a bit better, I would suggest doing strength training exercises. This really changed my life. There's a few weight training exercises that will help strengthen your back and correct bad posture. After doing these for a couple of months, my pain was greatly reduced and for some times, eliminated. It was never heavy weight - 20 lbs would do it, it's more about resistance and doing a lot of reps, getting the range of motion in and breaking up the tightness. When you're done doing some lifting, ask yourself if the parts that hurt are tired now? That's how you know you've targeted the right spots. For me, this one exercise changed my life (not my video, sorry about the loud music):

https://www.youtube.com/watch?v=-a9JBPQVKz0

After doing 20-30 reps, I would feel so tired in all the same places that used to hurt. Ask someone at a gym for help if you need (usually they will do it for free, if it's not busy, and just one exercise). It's hard to notice your form and if you're doing it correctly.

I would also suggest you check your ergonomics of your workspace. Are you standing or sitting? I've noticed that if I don't have an adjustable desk, I am always either too high or too low to be comfortable, and it's not great ergonomics. Get an adjustable desk even if you don't want to stand. Although standing can be helpful for maybe 5 - 10 minutes an hour. Don't try to do it all the time. Also, get a good chair. I have never been happier with a chair than my Aeron, and it was worth every dollar of the $1000 price tag. It has lasted years.

It sounds like from your post that the pain is mostly while you are at work, and not necessarily at home, although I'm sure the pain follows you. If you know what triggers it, sometimes that can lead to valuable clues. Sometimes it's my nervous habits that would do it, such as sitting strangely (like on my foot, legs crossed, etc) or leaning on one side of my chair.

If your pain is so bad, I would suggest not quitting your job, but asking your doctor for a medical leave of absence. That way you won't lose your health insurance, and you'll still get paid. That's what it is there for.

Sorry for all the rambling, but I wish you the best.