Since yesterday I have been having this sharp like pain around my belly button and every now and then I feel pukey. What could be the cause of it? Could it be a sign of pregnancy?

It could be about 20 things. Just not enough to go on, sorry. It could be anything from a simple stomach virus to appendicitis to something rare. (Yes, pain from the appendix can be felt far away.)
Why do you think you might be pregnant? Are you trying to be?