Genital region rash and pimples

Need help to see if this is some sort of STI. Had a feeling in my pubic hair area. Shaved it down to find at least a dozen red spots, looked like a rash. Some have now turned into pimples which look like they are filled with puss (white tops of the pimples). They hurt and the skin around it hurts too. The skin of my scrotum right below my penis is all stretched out and feel irritated like a rash but there are no bumps. Now my inner thighs have a rash of sorts too, I presume from my scrotum.

The shaft of my penis has nothing on it. Is this an STI or just a rash? If it is a rash, how do I get rid of it?