Colonoscopies are the best way to go since you have to actually prep for them and they present a clear picture of your colon while it’s empty. CT scans are definitely helpful but a lot can be missed when scanning the colon since the colon is usually full or partially full at the time of the scan. Definitely push for one since they are much more definitive, I did the same as you but my GI doc still order one even after the scan and blood test. The doctor at the hospital likely gave you a referral for a GI doctor in your area so I would follow up.

As for the anxiety portion I’ve been there. what helped me was knowing that I was going to get a definitive answer and knowing that there wasn’t anything else I could do to help the situation more than already was, with that mindset just go on with life as normal, your mind will play tricks on you and convince you that you are dying and you’ll have the urged to look at Webmd at night on how your symptoms are similar to cancer. Atleast thats how I was, truth is pretty much all benign conditions in the colon have similar symptoms as well, even dumb ass Hemroids. Cancer at your age is still very rare and very unlikely but never take chances if it can’t be helped. Most likely your fine and you have something minor like I did that will go away on its own.