Red bumps on penis

About 2 weeks ago I had sex with my boxers on, and while having sex it was a little sore I think from my boxers, but the next day everything felt fine, and had sex everyday after that with no irritation. Then a week ago I did the same thing with my boxers on, but the next day it was still irritated on both sides of the shaft, no bumps, or puss, or anything, and had sex the next 2 nights. then didn't have sex for 2 days, and the sore places are now small bumps, they look sort of like pimples without heads, but they look more like insect bites, and have what looks like a hole right in the center. And last night I noticed 2 more similar bumps closer to the head. I have been looking up stuff online, and they don't look like any herpes pictures I have seen, but don't look like anything else I have seen pictures of either. I was tested for std's in november and was clean, and have only been with my fiance since then.