This could be a bug. I've felt the same way for about 4 or 5 days. I could be pregnant, but it's not likely because it hasn't happened in the previous 4 yrs. of trying, but anything's possible, I guess. 4 or 5 hours probably won't spur ovulation, and a wk later is way early to already feel nausea. Sounds like you could've caught a virus or something.
As long as your taking the pill and NOT MISSING them im sure your protected, I took them for 10 years and never once took them the same time every day. I also think yes it would be too early to have pregnancy symptoms!