Are you sure it's tension? Might it be muscular? Is it affecting digestion or evacuation? Not everything is anxiety. But if it is, there are ways to relax your muscles that might not help your mind much but can help your body, such as yoga, meditation, exercise, breathing exercises. As the above says, ever tried therapy, especially CBT?
Well it seems you've been on a lot of different medications. Have you ever tried therapy? I hope I don't sound like a weirdo here, but ever try to control your mind?
Positive thinking helped me more than I've ever done. Telling myself I'm stronger then anxiety, I won't let this ruin my life, this is my one life I'm going to live it up, etc. (this helped with my health anxiety).
I'm sure you've tried therapy, but if not I highly suggest you try it. Also meditation.
Talk to people, have it be friends, family, or us on here. Many of us have anxiety or a history with it and will understand you fully with no judgement.
Heck I've had anxiety for 16 years. Some great years with minimal anxiety, some bad years where I thought anxiety would ruin my livelihood. Here I am now. Doing better, not perfect, but a lot better!