Looking for Super O, found regular orgasm

So after many months of using aneros, I finally started to notice some involuntary twitching and I could inch closer to an orgasm by breathing. Obviously excited, I continued with my breathing and contractions. After about an hour, I felt the urge of an orgasm taking over. I was really excited as I had thought I was finally on the right path to the coveted Super O. So I kept going until finally I felt 2 different orgasms. The first one was like a tiny dry orgasm followed by an actual orgasm where I ejaculated. This confuses me because I never touched my penis throughout the session and I was focused on my breathing and contractions the entire time. The only thing I can think of is it was making direct contact with my boxers but I wouldn't think there was enough movement or contact to push me over into a regular one.

My question is, how do I prevent myself from actually ejaculating? My goal is to have a prostate orgasm and continue to look for the Super O, I'm not sure if this experience was a step forward or a step back. Thanks!