At what age should I start seeing an obgyn?

From 13 to 16 in most countries. No reason to worry. You will only have an exterior exam and it won't last for long. The conversation might be longer especially if you have any issues like pains, irregular/missing periods..etc You will also talk about pregnancy prevention and transmitted diseases...etc

You should have already started

You should start seeing one once you start having sex.

My first doctor told me whenever I began having complications with that part of my body or first had sex.