The army website actually doesn't say much about learning disorders. Honestly, if all the doctors have told you is that you have a 'slow learning disability", I doubt it is too serious. Don't let labels like that hold you back.
Anyway, here is what I found that might help.
Possession of a high school diploma is desirable,
although not mandatory, for enlistment in any component of the
Military Services.
Overall aptitude requirements for enlistment and
induction are based on applicant scores on the Armed Forces
Qualification Test (AFQT) derived from the Armed Services
Vocational Aptitude Battery.