How do I know if I have acanthosis nigricans? Can I check for type 2 diabetes r something else? Got dark areas than my skin tone since 13 now im older

Take a deep breath. Acanthosis nigricans is a skin condition where someone has darkened velvety areas most commonly found in the skin folds of the armpits, groin and back of the neck. It is found more commonly in diabetes, but having the rash doesn't mean that you have diabetes. There are many causes for it. If you're concerned about diabetes, review with your doctor possible blood tests to assess for this.
Acanthosis/diabetes. Acanthosis nigricans is a skin change of darkening and thickening of skin at the back of the neck, in armpits and other skind fold areas. It is due to high circulating levels of insulin. This is in turn due to Insulin resistance which is a major risk factor for type two diabetes. It usually is worse with weight gain. One should get checked for type 2 diabetes: fasting/post meal sugar, hba1c.