how long will it take for me to get pregnant if ive only taken the shot once?

I have only taken the depo shot once and don't plan to take it again. I had my period once during the three moths and started spotting till the end of my three months on the shot. I had sex a week before my shot ended and then been having sex since with out a condom.. .will it still take me 6 months to a year to get pregnant even though i only took it once?....i think i am... i been feeling really sick..... could i be pregnant