I am having worsening panic attacks and am seeking advice

I want to apologize in advance for such a long post, this is something I've been dealing with for about 18 years now and it's weird and doesn't make sense and I have quite a lot to say on it. I appreciate your time.

I've been dealing with some sort of complex that is very serious and is gradually eroding away parts of my life. I've been seeing a therapist for a while now and doing what I can on my own and to try to find a solution, but have been unsuccessful so far and I'm really getting worried. I'll begin by describing the issue as it exists now, for brevity's sake I'll skip the history since I personally don't think it's relevant.

I am suffering from what I can best describe as gradually worsening panic attacks. There's nothing that I'm afraid of, I don't feel in danger and there's nothing on the line. But it happens anyways, and I'm simply downstream. These panic attacks are prompted by exposure to certain stimuli, almost always 'a large open space above and around me that I am aware of'; things like open freeways, theaters, large city squares, the interiors of large buildings ect. I am not afraid of these things, and in fact often think they're cool.

Once I am aware of such a stimuli, a counter starts ticking upwards. Some things add more to the counter per-second than others. The higher the counter gets, the more any given thing will add to the counter going forward; an exponential positive feedback loop. Additionally, the higher the counter gets, more and more things will qualify as a stimuli and add to the counter, resulting in runaway. In extreme cases once the counter is allowed to get high enough, simply being aware that I physically exist and that I'm in a place will increase the counter.

The higher the counter gets, the more panicked I become, and it will get quite extreme. I will shake, hyperventilite, cry (an otherwise emotionally secure 30+/yo) and try to get away and hide in a corner or a bathroom, or literally under a table. As far as I can tell, there is no cap on how bad this can get and I believe I could literally black out or worse if I can't escape the feedback loop.

The counter will gradually reduce over time if no further stimuli is present. It'll often reset completely after a couple hours, though in bad cases where it gets really high it can be days or even a week before things feel normal again.

When the counter is low, I can make a pretty good job of trying to supress my recognition of triggering stimuli, which keeps them from adding to the counter. At a certain point, however, once the counter does get high enough, I'm forced to acknowledge that I feel uncomfortable which further forces me to acknowledge the stimuli around me and a dam breaks open. At this point I'm on a timer and can no longer ignore my surroundings and start hyper focusing on avoiding stimuli, which causes me to recognize the stimuli more, hence the positive feedback loop.

Every time this happens, it's easier to happen the next time. It's becoming more and more prevalent every year and I need to stop it. I'm afraid as more and more things get counted as a stimuli, I'll approach a sort of singularity.

I personally identify this as some sort of wildly overreactive defensive reflex causing hyperfixation on things that further trigger the defensive reflex. I sometimes describe it as a memory leak, like you would see in computer science.

To speak personally, this has taken job opportunities from me, embarrassed me so many times going out and kept me from doing things I deeply want to do. I adore exploring, and space, conventions and beaches and big crazy cities. And driving, I never thought I'd say I miss driving but for the life of me I do. I can't barely do any of that now.

I'm currently on vacation with my girlfriend celebrating our anniversary in San Francisco, and I'm back at the room cowering away while she's out with the friends she wanted to introduce me to. I just had a pretty bad episode more or less getting lost in the downtown area with fireworks going off above me and all around the city.

I need to get home after this vacation, but I can't make that 6 hour drive. Best I can manage now is about 1 hour before it's unsafe for me to drive. So now instead of that 6-hour drive, I'm taking a 13-hour bus and train ride so I won't endanger myself, but I'm terrified about being trapped in this little metal room surrounded by windows and massive open vistas for 13 hours, with no opportunity to remove myself. My best hope is try to fall asleep early and hopefully wake up in time for the transfer.

I've always held that I don't want to medicate to treat this, but it's bad enough now that I've disregarded that maxim and am now exploring whatever might help. No dice on antihistamines or weed, looking into EMDR now. I don't know what I'm looking for here, but I appreciate any correspondence. Maybe advice, or point me in the right direction, anything would be appreciated. Thank you for your time and attention.