TTC #2

Im 19 almost 20 my and my boyfriend agreed that we are ready for another child. Our son is almost two. I have been on birth control since i had him until a month ago. My dr said its not likely i will get pregnant in the first month which i agreed upon but now im getting symptoms nausea, extreme fatigue, dizziness. My question is how long does it normally take to get pregnant after your off birth control? Could i already be? Or is it just my mind playing tricks on me