Depo Provera Injection

Hey, so I got the depo Provera Injection last month for the first time. I got it while on my period and had sex a week later with a condom. I haven't got my period this month and I don't know whether I should be panicking, is it normal for periods to be irregular/non existent after getting the injection? I used a condom aswell so was doubly protective? Should I be worried?