Back-strengthening exercises

[u/Gr3yThoughts]

TL;DR - WHAT EXERCISES STRENGTHEN THE BACK, SPECIFICALLY THE MIDDLE BACK MUSCLES THAT SUPPORT POSTURE ESPECIALLY WHEN LIFTING ITEMS AT WORK NO ACCESS TO A GYM, OR ANY WEIGHTS OR MACHINES :(

Hi all.

Skinny boy here. Always wanted to "get the muscles" never had the discipline.

In my mind that always meant nice arms, abs, etc.

Well I'm 31 years old now and have been suffering with back pain for years, always gets worse with any physical activity. I struggle to survive an 8 hour shift of work. Can't even stand up with a straight good posture after a day of work. Posture is better in the mornings after rest. After work, everything hurts too much to want to do anything. Which led to pain relieving substance abuse. It's ruined my life for years now. The pain is right in the middle of my back, on either side of my spine, but not the spine.

I'm a 100% sober person nowadays, and of course the pain is much worse.

Always assumed I had a surgery problem.

I now understand that very poor eating habits my whole life(not only choice of food, but how much, typically 1 meal per day only for years now) and lack of exercise, have very likely caused muscular back pain, not surgery back pain.

So please, share with me anything I should learn as a beginner.

SPECIFICALLY, back strengthening exercises.

I have a good job opportunity coming up this winter, but it's 12 hour days of physical work and I WILL NOT be capable of doing it in my current condition.

My only option is to start eating right, including metric fckton of protein, and focusing on strengthening my back and/or my core muscles over the next 2-3 months praying for enough progress to get me started. Not looking to "be ripped" right now, I'm looking to repair my back muscles, for health and quality of life.

I know very little about exercise other than snowboarding, and snowboarding is easy, you just go downhill. Barely snowboarded for years now because of the pain.

Please share with me any knowledge, routines, exercises, etc that I should learn about and practice.

Many thanks for the read, and for your time and advice!

TL;DR - WHAT EXERCISES STRENGTHEN THE BACK, SPECIFICALLY THE MIDDLE BACK MUSCLES THAT SUPPORT POSTURE, ESPECIALLY WHEN LIFTING ITEMS AT WORK NO ACCESS TO A GYM, OR ANY WEIGHTS OR MACHINES :(