Sorry you have to be here but you have found a great place for info and support!
I'm a Stage 4 and also had no family history and lived a very healthy lifestyle. I had a hard time even convincing my doc to order a colonoscopy because I was so healthy. He thought I might have a bacterial infection in my GI tract. In fact, the last thing he did before the colonoscopy was to reassure me that this was not going to turn out to be cancer!
Cancer is such a sneaky bastard.
Sounds like you're doing the right things and off to a good start, but here's a bit of advice.
If you have surgery, confirm that your surgeon is a board certified colon rectal surgeon, not a general surgeon.
Lynch Syndrome, MYH-Associated Polyposis, and Hyperplastic Polyposis Syndrome are all inherited types of colon cancer so you're not likely to have them since you have no family history. However, get tested anyway to make sure.
Other genetic tests you should have include: KRAS, BRAF, MLH1, MSH2, APC, MSH6, PMS2, and MUTYH. KRAS is especially important since it determines whether you can take anti-EGFR therapy like Erbitux. Additionally, testing for MSI or MRI status (MLH1, MSH2, MSH6, PMS2) lends information for the option to use pembrolizumab, a PD-1 inhibitor, and part of a new set of exciting immunotherapy drugs that are coming out right now.
You've had your CEA tested, but you might ask for CA19-9, LDH, and 25 hydroxy vitamin D tests also.
You have a port (smart!) so your veins are protected from the chemo. If you got a "power port" it can also be used for the contrast during CT scans. Your oncologist should have given you a bunch of meds (antiemetics, antidiarrheals, etc.). If they didn't give you a script for Ativan you might ask for it too. It helps with anxiety and nausea (2 for 1!). Make sure you stay hydrated after chemo treatments. Drink water, or even better, drink an electrolyte drink, even when you don't feel like it. This will flush the excess chemo from your body and make you feel better.
I know it's overwhelming at this point -- the shock of the diagnosis is more than enough to handle without the steep learning curve of treatment types, drugs, tests, etc. but hang in there. We have all walked in your shoes and can help answer your questions and concerns. Please know that you are not alone. I was diagnosed Stage 4 in 2010 and I am still very much alive and doing well today!
Hugs to you!