irregular period is late, could i be pregnant?

i'm almost 18 and my period is irregular. my last period started may 12th and ended may 16th. i probably should have gotten it by now, but i havent.
last week i was very irritable and had fits of rage, then i broke into tears and felt very depressed.
is my period late because i have been stressing out about whether i am pregnant or not?
i also skip meals frequently and try to eat less than 900 cals a day and i am 5'4" 114 lbs.