I recently had unprotected oral sex with a woman. About four days later I started feeling some mild discomfort in my penis. There's been no discharge, my bathroom routine hasn't been affected, and I wouldn't even really call the discomfort "burning". There are no other symptoms either. How likely it is that this is an STI versus something else? I currently have no insurance, so whatever can logically be done to address the situation without going to the doctor would be a good place to start if possible. Thank you!