HELP PLEASE

So I'm on the Depo shot. And the last two weeks I've had my period on and off. It would only last like 2 hours of so and then leave again. I recently got another shot and she said the bleeding was because my body went through the last needle faster. I've been really tired and stuff and my boobs are getting really sore. Could I possibly be pregnant from the 2 weeks of not being protected by the shot????