Was physical the the 5 th day then on 21st day of period and then again 4 days before period. Could I be pregnant.?

It could be. If you had sex without protection (condom), you need only one time to get pregnant. If your menstrual period is late, have a home pregnancy test or go to your physician. Remember that safe sex practices prevent unplanned pregnancies and protect against stds.
Yes. Ovulation typically occurs mid-cycle but not always. Home pregnancy tests tend to be accurate when taken at the time of the missed period.