I don’t think so man, you have a similar experience to what I am going through. Sometimes people just lose pigmentation in their skin on certain parts of their body. Vitiligo is a skin disorder that occurs in some people anywhere on the body and is not contagious, it just happens. Age might be a factor as well, if you are getting old then that might be another reason. Your body is going to go through changes forever. I know some people will scream HPV about this topic but you have to remember that HPV, even when it is flat or raised is still a hard wart. I have white spots as well but they are just a part of my skin. Sometimes I look at my penis and the white spots aren’t even visible so pretty much depending on the temperature of my body they are there or they aren’t. Hot they aren’t visible and cold they are more visible. For all you know you have always had these even before your sexual encounter, but when a person gets paranoid they search for symptoms until they find something they feel isn’t normal. If you have any disease, I would have to say it’s the same one I suffer from, and it is more of a mental condition. Your mind can destroy you man. Calm down and enjoy life, I’m sure you are fine. If you still feel paranoid the best thing to do is to go and see a doctor. Try googling this topic too, I read many stories where people are going through the same situation and everything turned out to be fine for them.
The only downfall is that sometimes even with medication it is very hard to regain skin pigmentation. The white discoloration represents the death of the melanocytes in your skin and once those skin cells die, it is kind of permanent in most cases. But like I stated earlier, you are not alone so do not feel bad.