the muscles of my back.

the muscles of my back are grouped into three major groups:
1. superficial muscles.  these attach to my shoulder girdle.
2. intermediate muscles.  these attach to my posterior thorax.
3. deep muscles.  these attach to my vertebral column.

it is my deep muscles that are bothering me the most.  especially on the left side of my spine.

https://geekymedics.com/deep-back-muscles/

A small note on nomenclature that makes learning the orientation of muscles easier: capitis refers to head, and any muscle with capitis in the name will insert into the head. Cervicis refers to the cervical spine, thoracis the thoracic spine and lumborum the lumbar spine. Respectively, muscles with these names will insert into the cervical, thoracic or lumbar spines.

according to geeky medics, these are the muscles of my back:

superficial:

1. splenius capitis

2. splenius cervicis

intermediate:

3. iliocostalis - lumborum, thoracis, cervicis

4. longissimus - thoracis, cervicis, capitis

5. spinalis - thoracis, cervicis, capitis

deep:

6. semispinalis -thoracis, cervicis, capitis

7. multifidus

8. rotatores

9. interspinales

10. interansversarii

11. levatores costarum

but I am sure that there is more, as I have looked at a lot of images of back anatomy now and so I must research this topic much more now.  but that is a very helpful start.  

https://www.kenhub.com/en/library/anatomy/overview-of-back-muscles

the muscles of the back can also be divided into two major groups: 

the extrinsic muscles of the back,

and the intrinsic muscles of the back.  

the extrinsic muscles of the back may be in the superficial layer or in the intermediate layer. 

the intrinsic muscles of the back may be in the superficial layer, deep layer, or deepest layer of the back anatomy.

Extrinsic Muscles (Superficial Layer)
Muscles: trapezius, latissimus dorsi, rhomboid (major and minor), and levator scapulae muscles

Extrinsic Muscles (Intermediate Layer)
Muscles: serratus posterior superior and inferior muscles

Intrinsic Muscles (Superficial Layer)
Muscles: splenius (capitis and cervicis), spinalis, longissimus, iliocostalis muscles

Intrinsic Muscles (Deep Layer)
Muscles: semispinalis (capitis, cervicis, thoracis), multifidus, rotatores muscles

Intrinsic Muscles (Deepest Layer)
Muscles: interspinales and intertransverse muscles

obviously there is innervation, blood supply, and differences in function.  

and there are origin and insertion points. 

and, yes,  there is still much more... so i got to take a break rather than go insane. ......