If i took my depo-provera shot once and didn't go back for my second dose i had unprotected sex could i be pregnant bcuz i spotted once and didn't spot again?

Depends: If your had unprotected sex within the 3 months of your shot then the risk of pregnancy is low. If unprotected sex occurred a couple of weeks after the next shot was due, then the risk of pregnancy is high. If you think you may be pregnant, do a pregnancy test and see your doctor. Spotting/ no spotting can be both signs of pregnancy or effect of Depo-Provera shot. Always practice safe sex use condoms.