The nature of your discharge can affect your eligibility for a VA loan. The Certificate of Eligibility process gets complicated for veterans separated from the military with a discharge other than honorable. In these cases the VA checks to see if the discharge was classified dishonorable.
If you had an 'other than honorable' discharge, seek help from your local VA office. It's best to get some expert advice on what additional information to file, where to send the paperwork and what to do if an appeal is necessary. Be sure to include copies of your DD214 form, plus any paperwork or documentation showing that you either didn't receive a dishonorable discharge, or had your discharge upgraded, modified, or corrected.