Well Lindsay, I don't mean for this to sound insensitive, but if you weren't getting a colonoscopy tomorrow, you'd probably still be freaking out about your polyp.
So often, our anxiety over our symptoms causes us to pursue medical testing, but when we get the very thing we want, we remain anxious. Do you see what I'm saying? Either way you're going to be scared. At times like this it's best to try and help yourself as much as possible. Don't make things worse by googling; start taking that anti-anxiety medication. Once you have your colonoscopy, then maybe it's time to look into anxiety treatment in earnest, before you pick another disease to fear and the cycle starts all over again.