Okay, well first of all: there’s no need to panic yet. The same thing happened to me all the time, it still happens now in fact. It’ll disappear for a couple of months and then it’ll come back like nothing had happened in the first place. However, I haven’t had sex cause I’m in a long distance relationship so that’s kind of out of the question for now.
Is there any reason that you could be pregnant? Have you been having any symptoms of pregnancy? Has it happened to you before?
You can go down to a clinic and they should be able to give you a free pregnancy test if you needed one. Technically they can’t tell anyone because of doctor-patient confidentiality, so if they told anyone they would be breaking the law. There’s no real way you can be 100% sure that you’re pregnant without a test. I’m sure you can find a way but until then, don’t panic! :]