boyfriend brake

So my and my ex/whatever are on a brake . We still talk and meet a few days ago I went on a date that was really good and lasted 15 hours witch in the end the guy went down on me@-@ I don't know what to do now. Feel abit bad but things with my ex have not been good for a while in the sack and I want to feel guilty but the other guy was just so good and nice . Should I tell the guy I'm on a brake with about this ?