If period was the 17th to 21st, and had sex the 26th and cycles have never been shorter than 30 days, what is likliehood of pregnancy?

Conception: If the first day of the menstrual period was the 17th, you had intercourse on cycle day 9. While often this is the first day of an ovulation interval, ovulation with a 30 day cycle would be occurring on cycle day 16. While it is possible to have conceived, the likelihood would be improved had you had intercourse closer to cycle day 16.