Temperatures can't indicate that you've ovulated for certain until about 3 days AFTER ovulation (when you have had high temps for 3 consecutive days). Yes, ovulation only takes place on one day, but after you release that egg, your temps stay high because the corpus luteum (it used to be the follicle that held the egg) begins producing progesterone. Progesterone is what makes your temps higher. The corpus luteum produces progesterone for about 12-14 days, which is long enough to sustain the uterine lining until either 1) a fertilized egg implants and lets your body know not to shed the lining or 2) nothing happens and it's time for a regular period.
The surest way to make yourself crazy (this might be empirically proven) is to study EACH and EVERY temp like it has meaning. STOP DOING THAT!!

You will lose your mind that way. It's important to remember you are looking for a big picture pattern: low temps before o, higher temps after o. your temps migh fluctuate several tenths of a degree from day to day but it's only (say it with me) THE BIG PICTURE that matters.
Also, if you're on birth control, you probably won't see any of these patterns in your temperatures, because the birth control will be supressing the hormones that make your temperatures change. If you are on birth control you shouldn't ovulate. That's what birth control does!