Opinions on my situation would be appreciated

I have currently been with my boyfriend for 5 years. Our relationship was good the first few years but recently it's become toxic! He does not like me going out with friends and has become extremely possessive and paranoid. I have tried to encourage him to join me on these days/nights out with friends but he refuses. Which obviously makes me feel trapped and unhappy because he will cause a big argument when I make plans to go out.

But over the past year I have been exchanging snaps with a "famous" music manager of a group I am a big fan of. 2 weeks ago he came to my city and asked me to meet him. I agreed and the next day I went to his hotel and we spent the day together. He said he is due to be in my city a lot more with his job and that we can meet again. He has a fiancé I must mention..

I do not feel guilty for this and I know most people would. I also know it is wrong, I want to tell my Boyfriend but I'm scared over how he will react because he has made past statements in the past such as "if you ever cheated I would kill you" or "I would ruin your life" Some of the friends I have told about this have said they wouldn't tell him. So I would like people's opinions or advice.