What Causes Nausea And Stomach Bloating While On Birth Control?

I have been on birth control for about 2 years now and missed my period last month. I assumed it was due to my birth control so I did not start a new pack this month but my period was about a week late this month but did eventually come. However I have been very nauseus for the past week or two to the point that I am sitting over the toilet dry heeving. I have only actually thrown up once though. I took a test before my period came and it was negative. Now that my period is over with I am still very nauseus and feel extremely bloated. Could I still be pregnant?