Threw up yellow acid-like liquid?

I ate at around 6:30 (some pasta). I had a cookie around 8ish. I took my birth control pill at 11:30pm ( I have been on BC since June, but I just changed it to a different brand monday...Low Ogesteral) and at 4:30am I threw up this acid tasting yellow liquid. No sign of food in the throw up... and it kind of sunk to the bottom of the toilet. The taste bugged me out all night. (yes i rinsed with water and mouth wash) but it was the only time i threw up. And I ate. So could it still be bile? im stuffyish sick right now. I had a sore throat last night.