I have shortness of breath and my breathing seems strange one week after stopping citalopram (Celexa). Is this normal?

I drink and smoke occasionally, but it's been a few months since I've touched anything. I have no known conditions or allergies, except for hay fever. I was prone to respiratory infections when I was younger (laryngitis, strep throat, etc.) but now I'm fine. No asthma or anything like that, but I don't have a very good cardio. Two weeks ago, Friday night, I started taking citalopram to treat my anxiety and depression. I have been diagnosed and prescribed other medications in the past, but this was my first time taking them. I was supposed to take 10 mg for a week and then increase to 20 mg. On Sunday morning, so after only two doses, I had some errands to run and I left home without eating or drinking. I got on my bike and at the first intersection I encountered, I started to feel super out of breath and nauseous. I ended up passing out on a little patch of grass (quietly, people probably thought I was just weird and taking a nap). I went to my pharmacist who told me to keep taking my medication, and that I was probably just hypoglycemic and dehydrated. I'm also not exactly fit and it had been a while since I rode my bike, so I decided to keep going. Other than that, I experienced pretty much all the "classic" side effects of Celexa (nausea, digestive problems, dry mouth, clenched jaw, muscle aches, inability to reach orgasm and reduced sensation, extreme drowsiness and fatigue, extreme anxiety, etc.). But on Wednesday morning, after my fifth dose, I woke up with a strange feeling in my chest at the base of my throat. It was as if I had something heavy on my lungs, a kind of ball. My heart was beating faster and I felt dizzy. Obviously, with my anxiety at an all-time high, I started to panic and ended up going to the emergency room. My EKG showed arrhythmia and tachycardia with an overall heart rate of about 140. They kept me under observation and did blood work, a chest x-ray and also tested me for Covid, as my side effects were flu-like. All my results were fine and did not seem to indicate any physical problem. They gave me Ativan and my heart rate finally came down to 90-100 because I was still very anxious. It's been a week since I took my last dose of Citalopram. I still have severe shortness of breath and now a dry cough, which seems to be worse when I am lying down. I also have extreme fatigue, and probably not directly related, I have patches of small itchy bumps around some of the areas where my blood was drawn (2 out of 8 locations, it took several times before the nurses could find a working vein...). I've read in several places that Celexa can cause breathing problems and flu-like symptoms, but is it normal for me to continue to feel like this a week after my last dose? Again, I only took 5 doses of 10 mg. Have you ever seen a similar bad reaction to SSRIs? Could it just be the withdrawal symptoms, even after such a short treatment? I'm getting a little paranoid that my Covid test was a false negative, even though I barely had any contact with the outside world before my symptoms started... I now have a prescription for Zoloft 25 mg, but I'm really afraid to start taking it after my experience with the citalopram. Thank you for your help.