Should I tell him I cheated?

ok so i was at my exs house and we were smokin weed and we both got reallllly messed up and ended up having . i felt so bad that ihad cheated. so i went back to my exs house to tell him we could just be friends and ended up getting drunk and rollin on molly and had with him again. ive had problems cheating in other relationships too, but i cant live with myself doing this anymore. i love my boyfriend with all my heart and were really close. im determined to stay loyal to him. his family invited me to their family reunion next weekend and i was wondering if i should tell him or not tell him or wait till after the reunion? idunno what to do please help!