HMmm. Well, predictable or not, sometimes our cycles go bonkers. You could have, for whatever reason ovulated really early in your cycle this month which means you may start earlier than normal.
You could just be experiencing some ovulatory spotting. The twinge in your lower right abdomen could've been a bit of a spasm which sometimes happens during ovulation. It does for me, and it feels mega weird!
You could also be pregnant. Though if you're using condoms correctly, I doubt it. I don't take hormonal BC either. I chart my cycles, use condoms, and try to abstain altogether on my highly fertile days.
If you are ovulating now, that means you should start your period on or around day 30-35. I would wait until day 35, and if you haven't started your period, take a home pregnancy test.