You are overreacting. Sounds like you caught a cold about 2 weeks after the sexual event. Conceivably a "small pimple" on the penis could be herpes, but if so, it sounds more like a recurrent outbreak and not something you caught from the event you describe. But see a health care provider if it persists or recurs, or if you remain concerned about your other symptoms.
Assuming you didn't actually flunk out and still are eligible for care at the student health clinic, go there. Most university student health services these days are highly expert about STDs, manage their patients very confidentially, and--trust me on this--they have heard it all. Nobody will bat an eye about your story, which is pretty tame compared to others they have heard.
Good luck-- HHH, MD
Ronnie