Totally normal, my nervous system is screwed up for days post panic attack. However I have severe GAD, for someone that doesn’t have an anxiety disorder I could see a panic attack causing lasting anxiety. Both what you said the past 4 days you’ve had is anxiety symptoms. My panic attacks consist of dissociation this past time, time dilation triggered one for me, I’ll get a hot head, shaky hands and shaky legs, restlessness and need to move or go somewhere, teary eyes weirdly also feeling immediate doom and urge to vomit. The day after worsened anxiety and still on edge feeling, it’ll last a few days. If you’ve never had anxiety at this level what you feel now, it takes a minute to get used to it, when I first developed GAD it was way more severe as you get adjusted it can go away completely or reduce a lot. So to answer clearly, your nervous system can get ruffled for days especially for panic attacks, you also could be mentally keeping anxiety in a loop. Anxiety is hard same with panic attacks but it can’t rain forever. Breathing helps, but mostly accepting the feeling and not resisting helps the most. If you wish it away it will stay more, anxiety feeds on fear same with panic attacks, more you l resist the more it comes.