What Causes Dizziness, Nausea And Abdominal Cramping While On Depo Shot?

I took the depo in August 2014. That was the first and last shot I had. Yesterday me and my boyfriend had unprotected sex. He stretched me some but it wasn t bad. Today I woke up with slight cramping. My periods haven t started back from the depo. I also feel kinda weird and nauseous/dizzy today. Could I be starting to ovulate finally? Could I be pregnant?