I Just Had My Last Depo Shot In July And

I just had my last depo shot in July and i was due again for the 3rd shot on October 3rd. I have been having mild cramping , like a period is going to start but nothing. I have noticed a few times when I used the rest room and wiped it looked like mucous with a pink tinge this happened for a couple times over a couple of days and then today the same thing but it was more brown. Is this side affects from going off the shot? Also I am wondering if I start the bc pill instead would they need to bring on a period so I can take it.