Is having six colon polyps removed unusual for someone who is just 28 years old?

Somewhat. Depends, if they were all small polyps with biopsy showing that they were hyperplastic polyps they have little significance, if however they are large (greater that .5 cm to 1cm) and adenomas that would be unusual and would require close follow up.
Colon polyps. Do you or your family have any of the familial polyposis syndromes? This would have been seen on your exam.