Got my period second week of feb, had sex using withdrawal feb 19-21. i took hpt 16 days after the last deed got negative. can be still pregnant?

Not likely: Pregnancy tests turn positive not before up to a week after potential conception, i.e., sex. 16 days after the last deed a pregnancy test is expected to be positive.

Probably not: Home pregnancy tests are pretty good. A negative test 16 days after last intercourse would make your risk of pregnancy quite low. There are some ways you could be pregnant an have a negative home pregnancy test such as an ectopic pregnancy. Fortunately these are not common. Best wishes.