I didn't get depo-provera shot in dec, had some spotting in march, and been having unprotected sex, and still haven't had a period could i be pregnant?

Yes: I assume your last Depo-Provera shot was in sept. Sometimes it can take 3-6 months for your periods to return to normal after stopping depoprovera (6-9 months from last shot). You will release an egg or ovulate before your first period, so you should consider yourself fertile now. Check an over the counter pregnancy test. If it is negative and you do not wish to become pregnant, start using birth control.