still bleeding

Its me, the obsessive-compulsive freak again.  I'm still bleeding, although there hasn't been very much blood today.  Its not very much, its only streaks.  I feel urgancy to go to the bathroom, and sometimes i go and sometimes i don't.  Sometimes its only skinny stool, which i know is a sign of cancer.  My anxiety is really getting to me and i don't have an appointment until the 17th to have the colonoscopy.  Is it totally unheard of to have colon cancer at age 18?  I'm totally convinced i have it, and the continual blood is only making it worse.  Its not a lot of blood, its only blood that streaks it.  Sometimes its mixed in with it.  I can't really pass gas either.  SallyA you were very helpful at my last posting.  Could someone please suggest something else this could be besides cancer?  I know that half the illness thats bothering me right now is the obsessive compulsive disorder, but i'm finding very hard to control my anxiety, dispite the medication i'm on for it.  My symptoms have been blood on, and occasionally mixed through my stools.  I haven't really had any stomach pain, but a little gas.  Sometimes my stomach is really acidy. Its not a hemmoriod or a fissure, and i've had the blood for about a month now.  thanks for anyone patient enough to put up with me!