I apologize if this is the wrong area to post this in, but I'd like some recommendations and help for this.

I'm a 19 year old male and I've been trying to deal with these acne that felt like hard lumps under my skin all over my lower back, red, inflamed looking acne with white tops which when popped would release cysts and oil or would, at the beginning, be completely soft, red and inflamed but would never get that white top and would turn into the hard lump from before and etch itself in my skin. The red, inflamed acne would spread across anywhere on my buttocks and sometimes to the sides of my legs, around the hipbone area. They sometimes appear in my stretch marks as well.

All of these acne were extremely painful to touch, to the point where sometimes I couldn't even sit properly, not to mention it made it worse.

A bit of history, which I don't know is useful to know but it did affect it a bit. I used to weigh a lot 3 years ago, and I've had double the amount of acne I have currently or even more, and those left a lot of hyperpigmentations or scars, I am not sure what they are, after they popped on their own even if I left them alone. (rubbing against the bed, or literally any surface considering they were on my back didn't help.) After I completed my weight loss, they significantly dropped, as said, double less than now, however they still pop out regularly although in smaller variations. Although, they're still as equally painful. I have excess skin and fat from losing so much, and they only appear in the areas where there's an abundant amount of it, contrary to my face, shoulders and chest where there's maybe bumps every once in a while.

Currently, only my lower back, up to the waist line, are riddled with underskin pimples. Anything below my back, on my buttocks and the sides of my legs, have a few red, inflamed pimples that I leave alone until they go away.

I clean and shower regularly, I do not excess clean the area, I sometimes exfoliate when needed. However I have a feeling it is caused by something I eat. While I was bigger, I ate too much sugar, which to this day I haven't cut off 100% and I still eat lots of it, which could be a potential cause. The issue is, even if I cut it off they still appeared although at slightly larger intervals than before so I am not completely sure.

I went to a dermatologist about this, which she prescribed clindamycin and benzoyl peroxide cream. The clindamycin did help somewhat but it didn't help prevent it despite being used regularly. Benzoyl peroxide helped dry them off however it also made my skin extremely dry, red and start bleeding if scratched, and they left scars or the hyperpigmentation marks.
Aside from that, she told me she would put me on antibiotics, however my family refused due to concerns about it and since then I haven't tried those.

Any sort of product recommendation for healing these and helping them prevent in general would be helpful.