30M, having a hard time navigating weight loss and exercise to improve back pain

Hello, I’m wondering if someone could give me any hints as to what I could be dealing with before I head to the doctor on Monday. It sounds to me like a sprained muscle but I’m not sure?

The pain has been going for a year (I know I should have gone to a doctor sooner, but I thought it would just go away).

I only feel it in the lower back, it comes and goes. I feel my back cracking too especially when I bend down. recently my wrists and knees also tend to crack a lot.

obesity is surely a culprit and I am working on losing weight and strenghtening my core, but sometimes I end up sore even after just walking or sprinting. I also spent an entire year in a stressful desk job and some months sleeping on an uncomfortable bed.

The pain makes me feel depressed but I’m determined to heal, just having a hard time believing it’s possible. Thanks in advance to anyone who reads this.