Change your locks - this behaviour is intimidation and intrusive.
Speak to your local police and ask for a domestic abuse officer to see you.
It may not be abusive behaviour (other than an abuse of trust) but it gets you on the record.
You see, most police shy away from getting involved in domestic, civil disputes, so this is a good way of having your problem on police files should the matter escalate.
Also get them to give you advice on improving security - it's should all be free. And ask them if they know of any local authority scheme to help you with this - most LAs have community safety officers who can advice further and may even offer a free lock changing/home security pack.
Also, go to a solicitor - and get some advice. Many will give you the first half hour free of charge.
DO NOT feel that you have to accept this behaviour, or it will happen time and again.