Ovulation does not occur 14 days before your period. Ideally, yes it does. But a 28 day cycle is also "ideal." DH and I were ttc for a year before I started charting my bbt. I went 2 months without ovulating. Then when I finally did ovulate, I ovulated on cd 14 (which would be indicative of a 28 day cycle), but I had a luteal phase of 12 days, not fourteen. The next month I ovulated on cd 21, and got a bfp at 10 dpo. Getting pregnant the day before your period is highly unlikely. The ovum only lasts 6-12 hours. Some women do spot around ovulation, but if it's heavy, normal flow you've probably missed ovulation. I am a firm believer of charting your basal body temp and cm. Good Luck!
Probably not although anything is possible. Ovulation occurs 14 days before the start of your period so you were probably getting ready to start and sex just helped bring it on. Have you started charting ovulation? That will be a big help to getting pregnant. I hope that helps.
The odds would be EXTREMEMLY slim.