Missed period for three months?

I’m 13 and I had my first period in August 2016. Every time I have get it, it lasts for about 10-12 days but it isn’t actually painful. The problem is I’ve only had about six of them and they are all about 3-4 months apart.

I’ve been really stressed the last few weeks though (a lot of school work), and I don’t know if I should try to talk to my doctor about it or just wait longer?

Please help.