Hey,
I was diagnosed with PCOS as well when i was 18. you may want to consult with your doctor about the symptoms. I have irregular periods to where i dont have them at all, rapid weight gain and i have abnormal hair growth that i deal with daily. I'm also on medicine for this, its in your best interest to contact a doctor.
I have very irregular menstral cycles my whole life I am now 31 and was sent to a specialist bc we are trying to conceive our second child and they found I have what is called PCOS (polycystic ovarian syndrome) meaning I have cysts on my ovaries which will screw up menstral cycles. I take daily medication for this and it is pretty common.
I would def go to your ob and talk with them about this and see if they can get to the root of it.