what forms i need to file for annulment

Annulment cases do not speak for themselves, unfortunately. There are specific statutory requirements you need to prove to be granted an annulment (incapacity at the time of the marriage, illegality (i.e., one party was already married), fraud, physically unable to consummate the marriage, etc. - see CRS 14-10-111). It actually is often easier and no more expensive to file for divorce, and you have to have a hearing for an annulment, while a divorce can be done on a non-appearance basis if there are no children. The forms for an annulment can be found at http://www.courts.state.co.us/Forms/Forms_List.cfm?Form_Type_ID=84. I help people with annulments and uncontested divorces on a flat fee basis if you would like further assistance.