I keep getting huge breakouts only along the border between my chin and neck. What could be the reason?

Hello everyone on the general discussion board. I am writing this post to ask for some advice because I have a terrible problem lately that makes me sigh deeply every time I look in the mirror. I used to take pride in having "perfect skin"—I never once got a pimple back in my school days. My cheeks and forehead are still smooth and free of blemishes, but I really don't understand why painful, red breakouts keep popping up specifically along the border between my chin and neck. You know those huge pimples that won't pop, swell up so hard to the touch that they hurt just from brushing against them while washing your face? Just when one goes down, another one creeps up right next to it. This cycle repeats endlessly, and now I'm even getting dark pigmentation on my chin, so I'm incredibly stressed out.

At first, I thought it might be a cleansing issue, so I paid extra attention to double cleansing, even getting under my chin. I also heard it could be due to shampoo or conditioner residue, so I make sure to tilt my head down low when washing my hair and thoroughly wash my neck with body wash. I even emptied out all my skincare products and switched to non-comedogenic ones just in case they contained pore-clogging ingredients, but there is absolutely no sign of improvement ㅠㅠ It’s driving me crazy because I have this all month long, regardless of my period, so I can’t just attribute it to my hormone cycle haha. It also seems to get worse when I don't get enough sleep at night or am under a lot of stress.

Getting an anti-inflammatory injection at the dermatologist does make that specific area clear up immediately, but since the root cause isn't addressed, it feels like pouring water into a leaky bucket—it's so frustrating haha. Is there anyone out there who, like me, suffered from this kind of chronic breakout only in specific areas, especially along the jawline, and then completely recovered? I'm wondering if I need to completely change my diet, or if I need to get sebaceous gland destruction or laser treatments like Agnes to stop the breakouts. Please leave a comment if you have any experiences or skincare recommendations ㅠㅠ I've heard that cutting out flour and dairy products is the surefire way to go, and while I'm at a loss as to if I can really live without bread and coffee, I'd be willing to try anything if it just helps my skin return to how it used to be. Please help me!!