It sounds like your husband wants to isolate and not socialize. You have every right in the world to accept invitations like the one to the barbecue. He's trying to isolate you, so you are totally dependent on him. He does not really believe that you are out cheating. That's just something to say to knock you. Good for you that you don't let him intimidate you from being involved with others. It must get a bit lonely, though, having a spouse who won't join you in a social life. What a drip.