“Is this a strange rash or a possible STD?”

I have had a rash that consists of small reddish dots in the pubic hair region for around 3 months. The weird part is that it does not appear on the genitals at all, only around the pubic hair area above. A doctor gave me a topical cream (clindamycin) and told me it was just razor bumps, but that did not fix anything. I also got a urine STD test and that came back negative. I am wondering, what could be the cause of this rash? Could it be another STD that wasn't tested for? Looking for answers here.