any ideas as to what might be going on?

This is my first post on here, but I was wondering if anyone might have any clue what might be happening with me. I'm thirty-five days late, which is two periods for me. I've had tender boobs more recently and some nausea around the ten day late mark, but I've never even kissed a guy before and there's no way I could be pregnant at all. My mom scheduled an appointment with her gynecologist for her to check me out in August. I'm a minor so I don't have one of my own. I've had my periods mostly consistent for nearly three years now and this is the longest I've gone without one, could something be wrong?