If you throw up the day after sex is that a sign that I am pregnant?

If you want to be pregnant, bad news: First symptoms don't appear until about a month after conception (eg when you had sex). You have to wait until you miss a period to take a test as pregnancy hormones won't show up earlier than that.

If you don't want to be pregnant, I hope you used contraception. If not, and it's less than 72 hours have elapsed since you had sex, you can take the morning after pill.

Final thought - perhaps you threw up cause you have a hangover?