HELP. My dog is afraid of everything?

a loud noise must have hurt him or scared him and it's leaving lasting marks on him so he's scared every time he hears a loud noise. I suggest every time he gets scared over a loud noise tell him it's ok and comfort him. Let him know it's safe and it's just a noise. Bring the vacuum near him not turned on and let him see it and say it's ok. Give him a treat when he doesn't get scared as positive reinforcement and distract him or keep him happy while a loud noise is taking place while telling him good boy etc. Don't force him to feel ok though if he's still really scared. Your dog has to get over the fear himself and forcing it on him may just traumatize him more, be patient