21M Experiencing Recent Onset Back Stretch Marks & Pain – Seeking Medical Perspective

Hello Doctors,

I'm a 21M (169-170cm), (62kg) from Iran hoping for some insight into recent physical changes I've noticed, primarily concerning my back.

Background:
To provide some context, I had a somewhat atypical development. I was born at a very low birth weight (900g) and experienced puberty, including a significant height spurt (around 9-10cm), quite late, between 18-19 years old. My father is 180cm, and my brothers (different father) are also tall. I developed acne around age 20, and my beard is still developing (though minoxidil has helped recently).

For the past 1-2 months, I have been using Human Growth Hormone (HGH). Very recently (within the last couple of days, coinciding with an increase in pain), I introduced an Aromatase Inhibitor (AI) to my regimen. I also supplement daily with calcium, vitamin D3, and zinc. I engage in daily jumping exercises which I feel target my core and back.

Symptoms (Recent Onset - last 1-2 weeks):

1. Stretch Marks: I've noticed the appearance of new vertical stretch marks along my spine, and an increase in the prominence/number of pre-existing horizontal ones on my back. These are all light-colored/white, not pink or red, but their appearance or increased noticeability is very recent.
2. Pain: Significant pain in my knees and particularly my back, which can be quite intense, especially at night.
3. Altered Sensation: The bones in my back, particularly along the spine where the vertical stretch marks are, feel subjectively "different" to the touch – perhaps more defined or the surrounding tissue feels denser, it's hard to articulate precisely.

My Question:
Given my developmental history (late growth spurt), my current age, and my current regimen (HGH/AI), could these recent symptoms – the new/more prominent stretch marks, the pain, and the altered sensation in my back – be indicative of ongoing growth (skeletal and/or muscular) or other significant physiological changes in response to these factors? I'm trying to understand what might be happening physically.
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Image Attachment : https://imgur.com/a/1KAZNgj

Note: My wrist growth plates are closed, checked through x-ray; other plates aren't checked.