Do I have penile ringworm?

I noticed I have 3 or 4 red rings on the shaft of my penis on the underside. They don't really itch, but I have never had ringworm so I don't know if it is or not. I went to the Dr. and she told me that it could be ringworm, but didn't tell me what it could be if it weren't. She also mentioned that if the clotrimazole cream she gave me didn't work, then to come have a blood test done. This kind of worried me because I have been sexually active. I always use a condom when I have intercourse and they have never broken. I did receive unprotected oral once without a condom, but these rings starts showing up a few weeks after that and the Dr. told me a few weeks before(after the sex) that I was STD -free. I think it might just be ringworm because I was just on a long vacation in Thailand and is was really hot and humid there and I was sweating profusely. Does this sound more like ringworm from sweating in Thailand or something more serious? Any Drs. on here?