I think you will need to contact him somehow. Not for his benefit, but for the safety of the public as a whole. I feel like we as humans have certain obligations that extend beyond interpersonal relationships, and this is one of them.
Believe me, I can feel your pain. My ex never would've confessed to
any infidelity if I didn't have a positive test result to throw in her face, so I was actually looking forward to a positive result. Of course I had symptoms, so I knew I would've tested positive to something, but I remained very worried about what
else she might've given me (fortunately nothing that wasn't cured within a few days.

) It was still a very nerve-wracking week while I waited for my appointment and then waited several more days for the final results.
Hang in there. The next several days will most likely be very anxious and difficult, but you are definitely doing the right thing in getting tested.
Also, you should check with your doctor, but most places will allow you to anonymously contact previous partners alerting them to the need to get tested. That route may be a better one for you to take (should you test positive for anything.)