It's never an easy conversation but just start out with - "we need to talk about something rather delicate - I noticed something unusual on my genitals this week so I went to the health center and they've discussed with me the possibility that it might be genital herpes. I'm waiting for my test results but I think it's also important for you to go get yourself tested to so we know who has what and can take appropriate precautions if needed - I have no idea if it's even herpes or how long I might've had it - this is the first time I"ve ever noticed anything unusual on my genitals but from the reading I"ve been doing lately I've found out that what most folks assume is a new herpes infection is actually just the first obvious reactivation of a prior infection so I think it's important we both get tested and share our results with each other." That way you aren't being accuastory and are still presenting some facts at the same time. As someone who never knew she had genital herpes until she passed it onto a partner and he told me - I really did appreciate his being able to come to me and talk to me about it even though it was pretty akward. I truly had no idea I had it until he came to me.
Chances are good that your lesion culture is going to come back negative so don't be surprised if it is. I'm guessing your school doesn't offer the pcr swab as a way of testing for herpes and you've had this lesions for over 48 hours now so the chances of it coming back negative are pretty high. Did they only draw blood for syphillis or did they also draw for herpes? If they didn't do a blood test on you too - definitely look into getting one. If they don't offer a type specific herpes igg blood test - you can check thru www.healthcheckusa.com
to order the herpes select igg for hsv1 and hsv2. I don't know if they offer discounts for college students but it certainly never hurts to ask.