I've had the shot. i was supposed to return to get the shot april 16th. i had unprotected sex on the 28th of april. can i be pregnant?

Pregnancy unlikely: The protection of a Depo-Provera shot does not vanish in 12 days, but lessens over time. However, one can do a pregnancy test. A urine pregnancy test, done correctly, gives a reliable result 3 weeks after sex (3 weeks after when conception might have occurred). If done sooner, a positive result is likely real, but a negative result may be due to testing too soon, and thus lead to a repeat test.