I'm 21 and vomiting at random times, and I'm sure that being pregnant isn't the answer. I got my tubes tied after my last baby was born.

So,, you are asking why you are vomitting. Can't really say as we don't diagnose on the internet; are you subconsciously trying to lose weight and this is bulimia? Sometimes this is the way it starts. A very dangerous activity.

Go to a doctor, have him diagnose after a physical exam and blood tests to make sure it isn't anything that would be worrisome.

Are you taking any medications? Sometimes nausea is a side effect from some medications. If not, I would go to the doctor as soon as possible.