I Gave Him My All and He Cheated On Me

I did....and he did....
and now...after 3 years....I think I can't do it anymore...I can't keep going....I tried...I fought....I fought for years...and now...I just don't think it's in me to keep fighting....I really feel like my feelings for him have gone...I just don't have it in me....I just have to go...its not fair to him...or me...to keep up this show...and I'm scared...this marriage is all I have known for 27 yrs..and it's scary.....