I Have Nightmares

Please indulge me in this one. I’m writing this as a bit of therapy and in the hope that it can move me forward past an impasse.
I have nightmares.
Sometimes I don’t get one for a while then they’ll come back night after night and I wake up in fear, until I remember after a few moments that it can’t happen, but the fear lingers on for a while into the day.
The nightmares change location, but they always have the same storyline. I’m going about my life as it is now, happy, content, and then my ex husband reappears.
In the dream he threatens to wreck my new life. He comes into my home, takes food from the pantry, lifts and discards the knick knacks about the rooms and snickers to himself. Sometimes there is an unknown woman with him, at other times he’s alone. He never looks at me in the dream, always averting his eyes, and mostly looking directly to the right or the left so that I only see him in profile.
I shout and scream at him to leave, but he ignores me. I try to push or punch him, I pick up heavy blunt instruments to hit him, but he seems to have an invisible shield and I have no power. Nothing connects and they glance away. With all my power and might I’m still at the mercy of his horrible whims. Even when my husband and family are present in the dream they seem unable to intervene, like they are behind a veil.
Eventually he always walks out, leaving the front door open, telling me that he’ll be back, and that’s how the dreams always end.
I’ve tried to seek information on how to deal with this. Mostly people say that you should face up to your monsters in your dream and thereby conquer them, but that doesn’t apply in this case. I do face up to him and I’m impotent to stop him. One thing I read says that this kind of nightmare is typical of post traumatic stress disorder.
Certainly it was an unhappy and at times abusive marriage for most of its 12 years, and the breakup was extremely unpleasant, but I haven’t seen him for nearly two years. He’s never taken any real interest in our son, and in real life there’s no way he could wreak the havoc that happens in the dream.
His behaviour back then did create fear in me because there was never any rhyme or reason or pattern to it. It got slightly worse, as in unpredictable, after we split up. You can get a measure of what it was like when I can cite occasions like the one where the police phoned me up during one of his access visits to warn me about him and recommending I go retrieve my son from him straight away.
So, how do I stop this? How do I get past this? It’s been seven years since we split and I’m really over these dreams. Does anyone have any advice, any pointers on how to put to rest the last of what was a very unpleasant period in my life?
Thanks for reading, and have a great week.