hi delr. i don't think it's possible that you're pregnant. i do think it's possible that your depressed though. the symptoms you're describing (even the late period) can be related to stress and depression.
my suggestion for you:
let go of the worry. all the worry in your life. let it go. if you are a religious person, then ask God to take the worry away from you. if you are not then just let it go.
here's the thing. if you worry about something, 99.999% chance it won't come true, so what good did all that worry do you? ZERO. ok, so let's see...the 0.0001% chance comes true. what good did it do you to worry about it? zero. worry sucks, its a waste of time. learn this while you are young and you'll have a pretty good life.
jasmine