9. Flu-Like Symptoms
If you are experiencing flu-like symptoms such as headache, fever, swollen lymph nodes, and nausea, it might be the flu. That said, it could also be something much more serious. All of these symptoms occur when your body is fighting off an infection. If your body is trying to fend off the early phases of Syphilis or HIV, these symptoms might be your only clue. Therefore, if you engaged in risky or unprotected sex within the past six months, you might have something other than the flu.