Im On The Mini Pill Known As The Progesterone Only

Im on the mini pill known as the progesterone only pill. For the past few weeks I've been having migranes every single day and been feeling sick with it. Im also getting little cramps in my tummy. I gave birth to my daughter 3 months ago. I had sex and after I had one little spot of a really light pinkish watery discharge. I don't know if I'm pregnant or not or its something else. What do you think it's is?