Worried about rising CEA levels

I was diagnosed with colon cancer in 2009. At that time they removed 1/3 of my colon. We did blood screening through the Mayo clinic and they came back that I had a predisposition for polyposis. The cancer had not gotten out of the colon area. Over the next 7 years I was having regular colonoscopies and the doctor removed polyps every time. He recommended that I have the reminder of my colon removed and attache the small intestine to the rectum. That surgery was done January 2016. Up until this surgery was done my CEA levels were in the 3-4 range. This past April I was in to my oncologist for my check-up and my level has increased to 6.1. We redid the test again in 6 weeks which was yesterday and they have increased by 0.3 to 6.4. I was wondering if anyone else has had this problem? I have had my mammogram done and it is clear, I don't have any more colon so it can't be colon cancer, I had a hysterectomy when I was in my 20's so that rules out ovarian cancer. Any help with this would be greatly appreciated. Thanks in advance.