What Causes Delay In Periods Along With Diarrhea And Vomiting?

I had a baby 3 months ago and my doctor put me on a birth control pill when it was time, It made me feel horrible and I bled for a whole month so I stopped taking it after a month of being on it, While I was on the pill I always used condoms and since Ive gotten off of it I have continued to use condoms. I have not gotten my period for a month now? is this normal? could I be pregnant?? Or is my body just completely out of whack right now because of the baby and stopping the pill and bleeding so much??? I have also Had bad diarrhea and vomiting, Is this something to worry about or is this just probably a stomach bug???