Should I do DNA Test?

for the sake of truth it would probably be best for you to have the DNA test. it would be the only way to be sure. if he really is you're dad, then he has the right to know, that goes for you too. also, whatever the result may be, there shouldn't be any regrets for mourning your deceased 'father' becauses he was and will always be your dad, maybe not by blood, but by the love he showered you when you were a baby.