[wonderbread]

If your on birth control and you took the morning after pill your chances of being pregnant are very slim.
It also is a little too early to tell. But if you continue to feel like this for a while and don't get your period the best thing you can do is take a test.
It could also be you are coming down with something and your period is close.

That is why it is important to use every possible type of protection you can so you don't have scares like this.