Please help! i am scared, what is wrong with me?

i did not get my period this month and i'm not pregnant (i'm a virgin) and i'm not starving myself (which are two reasons why people lose their period except for menopause) the last time this happened to me was last june i was really stressed (which is another reason ) b/c of finals. but doesn't it take a LOT of stress for that? and for the past two days my right eye has been twitching. is stress the reason for this? is there anything ele that can be causing this? should i see a doctor about this? i am only 15 and going to turn 16 in a month