You had no risk with the oral sex. Condom fallen off?. If you lost the condom upon withdrawal, you had no risk. But if had continued the penetrate without condom, you definitely had a risk there.
Tested at 15? 15 days or 15 weeks?. If you meant 15 days, I'm afraid it's a bit too early. But at this moment any negative result is a good indicator. The recommendations per the CDC would be the Duo at 6 weeks followed by a 12 the week ab test would conclude your status.