Intense anxiety is awful

There might not be any specific thing you are "worried" about for it to come on. It could just be the change in the sunlight/weather bringing it on.
I have found CBT to be brilliant for my anxiety. Not the 6 sessions of CBT people in the US get, specific longer term CBT for anxiety. Also there are SSRI's that a great for anxiety. Zoloft works best for me, but its different for everyone.
I also like tension tamer tea, I have been on a lot of meds in my time and that stuff works just as well if not better than some of them.
Its really great you see this for what it is and not blindly following the pdocs saying you are manic, I bet you arnt the only one unfortunately. I hope they dont drug you up and actually listen to you instead of sticking the manic label on.
I really feel for you being locked up for something so simple to treat, if only the docs got it right!