I can not use Preston as a companion or even talk to him all he does is give missions to do for the minute men, did I wait to long to use him "tried to use him before Diamond City" or is this a glitch?

I'm having the same problem.

YouTube video: /watch?v=_dyz3CyT6k4&spfreload=10

you are def not alone... i was unaware i could even get him to tag along with me for a while... thought his main purpose was to just give me lame quests over and over again, until i got to looking at the perks offered by companions and how much his would help when im getting swarmed by feral ghouls... but alas i cant get his useless ass to follow me anywhere so :/