QUESTION TO GIRLS! My period has been really irregular.. I'm concerned and I don't want to spend money to see a doctor?

I got my first period my freshman year in HS before spring break (April 2013), then I did not get it again until almost a year later (April 2014). My third period came 4 months later (August 2014).. and I haven't gotten it for 5 months (Jan 2015). I am currently a junior in HS. Do any girls have this problem? What did you do?
QUESTION TO GIRLS! My period has been really irregular.. I'm concerned and I don't want to spend money to see a doctor?
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