Don't be scared. Concentrate on getting the proper diagnosis and having all of your questions answered.
See a doctor that will do your colonoscopy. That's your starting point. Depending of what is found, you will likely be referred for blood tests and a CT Scan.
Should cancer be found, please see doctors that are part of an actual cancer hospital. No clinics.
I wish you all the best and maybe things are not as bad as you are thinking!
Your starting point is definitely to begin with the colonoscopy.
Ask questions, get answers and hopefully you feel confident in your doctors. If you don't, find another before you get far into this.
Don't be scared.
Being concerned is good.
May you find strength in this journey and have faith in the outcomes for a healthy life!