I had unprotected sex on febuary 16 2021 one time only is it possible that i can be and or get pregnant?

Yes: Once is all it takes. You should know 2-3 weeks after the event when a urine pregnancy test would first turn positive. You may not. The average wait for a desired pregnancy is 6 months of trying.

Possible: Conception occurs within day or so of the sex. It takes about 3 weeks for the embryo to make enough HCG for a positive pregnancy test. Blood test may be done a day after a missed period. Home pregnancy tests should be done 4-5 days after the missed period. If the result is negative repeat the test in 4-5 days. Use first morning urine and follow instructions for the test carefully.