You've described the classic pattern of something that isn't acne: Malassezia (pityrosporum) folliculitis, an overgrowth of a yeast that normally lives on everyone's skin. The tells are exactly what you listed — monotonous same-size bumps (acne is usually a mix of blackheads, whiteheads, and deeper spots), itch, a forehead/chest/shoulders distribution, flares after sweating, and a stubborn refusal to respond to standard acne treatment. A review in the Journal of Clinical and Aesthetic Dermatology describes this presentation and how routinely it gets mistaken for acne, sometimes for years (https://pubmed.ncbi.nlm.nih.gov/24688625/).
The reason your three months of products did nothing is mechanistic: benzoyl peroxide and retinoids target bacteria and clogged follicles, not yeast. When the diagnosis is right, antifungal treatment tends to work quickly — which is also why this is genuinely a see-a-professional situation. A dermatologist can confirm it (and rule out real acne, or both at once, which happens) and the correct diagnosis changes the entire plan.
Meanwhile, it helps to shower soon after sweating and skip heavy oils and rich creams on the affected areas, since the yeast feeds on certain oils — though the ingredient-avoidance evidence is weaker than the diagnosis-and-treatment evidence, so treat "fungal-acne-safe" lists as a heuristic, not a cure. Our fungal-acne checker (/check/fungal-acne) can flag commonly-implicated ingredients in your current products while you wait for the appointment.