I have dyspraxia dyslexia and a heart murmor but all of these conditions are very mild i was wondering if i could join the army, (I highly doubt it) 
American–No way.
British–Quite possibly. from what i've seen overseas, you don't have to do anything or be tactical to be in the army. you just have to be scared to shoot back at the enemy in fear that you will die.
Not in the British Army, you have to be fully fit.