What do I need to do?

So, just had an annual exam and got all the tests done. I've been tested for STDs before through a urine sample and never came back positive to my knowledge. I just heard back that I tested positive for one and that my bf will need to be treated as well. He has never been tested before.

What's the best way to go about telling him? Naturally I'm worried he will be upset, but I'm thinking he had to be the original carrier due to my testing negative prior. What other people do I need to tell or do I need to?

Sorry if any of these are stupid questions, just a little anxious about the whole thing.