5 weeks on sertraline and panic attacks

My psychiatrist prescribed sertraline because I have generalized anxiety disorder and frequent panic attacks. My initial dose was half a pill, which I instructed me to take for two weeks to lessen the side effects. The first few days were rough with nausea, but after a few days I felt better (perhaps a placebo effect). After those two weeks, they increased my dose to the full pill, and I've been having terrible panic attacks. They've woken me up in the middle of the night and were so intense that I felt like my chest, arms, and head were burning. I was terrified because I'd never experienced that symptom before. It's difficult to control myself because I truly feel like I'm going to faint or die. Every day I feel anxious and restless, afraid of going crazy, having lucid dreams, and sensations of being on the verge of a panic attack but without actually having one. I also have weakness in my legs. In this episode, I felt like I was about to faint. I've checked my vitals, and everything is fine. I've felt awful all morning. My fear and concern is that last year I was taking the same treatment, 50mg of sertraline. I took it for many months and it helped me a lot, and I don't remember feeling as bad as I do now. I don't understand why I feel like this now; I'm supposed to be getting better after three weeks, not the opposite. 😫