I'm fifteen, still a virgin and this has happened before once.
Right when I though about going to the doctor I got it one day.
After that one week though its been 3 months since.
I don't find this normal. Can someone tell me what this means or what I should do. Thanks.

It's always the best to ask the Doctor. For teenagers, it is normal to have irregular periods for years after the first menstruation... but the doctor knows best. There is always a chance of something going undetected.