hi well at 17 your still at that age for your periods to do this stop and start it does happen and for gaining weight and on top of that getting acne. try seeing your doctor for a blood test for your hormones they could be out of whack and a blood test tells all. do hope this helps you. good luck
i'm 17 and i haven't had a period in 3 months. dont know why. looked into poi not sure if it's it but i have the symptoms. i've also been having period cramps for the three months. i've gained about ten pounds and i'm getting acne which is abnormal for me.