| | Re: How to get through to him?
Take him aside and ask him what is going on, either he trusts you and he stops behaving the way he does or you do things as a couple –even if he does not like it, put on a charming smile.
e.g. the babysitting scenario, he can sit with you and when it is your turn to go out he can join you, if your other activities are a concern for him he can accompany you and watch.
He may have valid a reason doing what he is doing if so he should say.
Simple answers I know but it is going to get worse, if he is so suspicious take him to a councillor, take evidence and examples of the incidents include the times and dates otherwise he will deny this.
If he declines to go to the councillor let him know that you are going get their advice on this.
If this fails you either live with it or leave
Or if it was me, I would do the same to him, walk in pick up his phone and start checking the text messages, check his speedo reading and of course let him know your are suspicious because innocent people do not behave the way he is behaving.
Always let him see your phone texts if he asks, have the passwords to your email and other accounts, there should be no excuse for his behaviour.