I'm a 21 year old girl and never had a boyfriend. One thing that puts me off is..?

Wow, you sound really paranoid. A friend in the clinic? Um, why don't you just tell him where to go, or to get it from his own physician? Getting a test later on is NOT breaking trust either because some tests don't show the disease cuz it's too early. What are you going to do when you get married? Just never have sex?