Ok, here is the problem.
There is a method for seeking an upgrade, called a DD Form 293 through the discharge upgrade board. It gives you the best chance to have an upgrade, you can only use that board for 15 years following your discharge.
If you can manage to file that DD Form 293 before you hit 15 years from the date of your discharge, you have a chance. Not a great chance, but that's nothing against you. They just don't upgrade many, but they do upgrade some and people with a solid life history since separating have the best chance.
But you have to hurry. You need to obtain your military records, fast. I would search online (I can't advertise for them, sorry) for fast military records search and work with an agency there is St. Louis. They can get your records very quickly, usually a day or two. I would also consider hiring an attorney to submit your application quickly, so that you can get it turned in before the deadline of 15 years. Just search online against for "attorney" and "DD Form 293."
If you can't make that time frame, it's going to be nearly impossible to get the discharge upgraded. That is because the only option after the DD Form 293 time frame passes is the DD Form 149, military records corrections board. They almost never upgrade discharge, and only do so if you can show that the discharge was an injustice or error at the time it was given (because they are just seeking to correct military records, not upgrade discharges).