Hi Rain,
I can totally relate to the anxiety appearing after having kids. I do think that hormones can trigger anxiety. I have no medical proof, just experience. When I was pregnant with my second child, the anxiety got really bad for me and then in the post partum phase, I was completely at my worst. I also have my anxiety start to take over when I have PMS.
GAS is hard because, as you say, it seems that there is not really a specific situation. But, just to ask: are there any triggers that you can pinpoint at all? Like, is it crowds? Being alone? If so, you can then take one (yes, just one) and practice challenging your thoughts.
To answer Ashley's question about what works for me when trying to get through physical symptoms: It seems weird to me, but sometimes, I try and ride it out like being on a surfboard on a scary wave. I think, "Yeah, okay, I feel weird. It's okay, it will pass in a bit. What could be making me feel like this? The lights? I'm tired? Just hang on. Look for the signs that I feel better." Then the moment I feel even slightly less anxious, I dwell on that instead. "Okay, I feel a bit better already. It's all good. The panic is going away." And then I look for things around me that make me feel relaxed (e.g. look out a window).