@Immyreeve91
I am torn, because in some ways, there is no need to tell him, as it was 6 years ago, and it would only upset him, and would trash your relationship.
OTOH, is there any chance you (when you're with your DH) could bump into this bloke you cheated with?
I did know a man (he was a friend of DH's some years ago,) who shagged another woman behind his 'then girlfriend's' back - they had been together a year, and got married a year later.
They bought a house 3 years after getting married (and 4 years after he cheated,) and who did they discover lived 3 doors away from them a week after they moved in? The woman he shagged!
Long story short, he ended up telling her about cheating on her with this woman, because he didn't want the 'other woman' telling her. It destroyed their marriage.
His wife said she wishes he had told her when it happened, then she wouldn't have wasted the money and time and energy marrying him, and spending 3 or 4 extra years of her life with him! Thank God they had no kids together!
I am also concerned (like some other posters) as to why you are still dwelling on this 6 years on?
You need to think very seriously about what you do next. Because this is never going to go away.