What Causes Irregular Periods,discomfort In Stomach And Excess Burping?

Hello, so I had sex and he pulled it out but I still took plan B bills. It's been about 7 weeks since, I haven't had sex or anything. I had my period in the time I was suppose to but it was short, only about 2 days. And now I'm getting bubble feelings in my stomach, and I'm burping a lot but I dont usually burp. Please help