Need answers please!

Okay so I took the depo shot one time and it expired in August, and I recently just got my period back last month. I was supposed to start this month on the 3rd and still haven't, we've been having unprotected sex for about two months now. Do you think my body's still adjusting or could I be pregnant? Sometimes I do get nausea and dizzy, and I've been having headaches more frequent. I've also cramped a little bit the past week but no signs or AF. So can anyone help me please!