feeling nausea at certain food i ate

Hi mummies. Recently some food that i eat i would feel nausea and i just stop eating the food. Why isit so? Not sure whether im pregnant as i just gave birth 6 months ago. And my period hasnt be really consistent but it came every month. Its just late for a few days. Last period was around 20++ oct (cant really remember). Until now, i have yet to get my period. #advicepls