What Causes Missed Periods And Abdominal Pains?

hi, I m 18 years old and I ve missed my period two months in a row now. I m not sexually active and I ve struggled with ovarian cysts. this month is different because I m not showing any signs of a period, no cramps, bloating, or tenderness but when I pee its kind of a yellowish tent and when I whip it s brownish red. I ve had horrible headaches, lower back and abdominal pains like I would with a cyst but it goes away after a few hours, I ve peed way more than normal, and seem to have a loss of appetite. id like to know what you may think before going to a doctor. thank you.