So me and my boyfriend are going away for a week we don't live together and don't see each other that often so I am or was looking forward to it until I over heard him telling someone he had invited hi friends along!! Why didn't he tell me or ask me if it was OK!!

Why didn't he tell me or ask me if it was ok!!!!
Don't know! But maybe you should ask him instead of the internets!!

Yes, ask him. Sometimes we think stuff is OK because it is OK with us without realizing that it might bother you. Talk to him about it.

Invite some of your friends too.
Be careful though - sometimes what you overhear is just joking.

Talk to him. If you're in a relationship you should be able to have a conversation with him and tell him what's bothering you.