I've recently performed oral sex on my boyfriend. The first couple of times I did it, we used a condom, but then I wanted to try it out without one. He was comfortable with the whole thing so it wasn't a problem. We've been together for over a year, we know each other very well now and our personal preferences. He's also my first sexual partner and I'm his, so he has no history of other partners. But is there still a chance I could get an STI?