What a terrible ordeal. I’m so sorry you are so very distressed. People don’t all respond in the same way to smoking weed — and not all weed is the same. Sometimes something else has been added to it.
I hope you saw a medical doctor during the time you were so sick to see what was wrong physically. I also hope you learned that you are not someone who can use.
You were already evaluated by a psychiatrist; someone with years of training as a medical doctor with a specialty in mental health as well as probably years of experience. The psychiatrist is in a much better position to assess you than you are. Since the psychiatrist has talked to you in person, his or her opinion is far more valid than any of the generalities you read on the Internet or any conclusions you reach on your own.
From what you wrote in your letter, I’m guessing that you are exceptionally suggestible — meaning that you take in information and apply it to yourself it much more quickly than the average person. You don’t seem sufficiently able to weigh the information or the source it comes from with objectivity.
One of the hallmarks of panic disorder is the fear of fear. Panic attacks feel terrible. It’s not unusual for someone who has had one or more to then start to fear getting another one — which only helps bring it on. You need help to break out of this cycle of fear.
Please go back to the psychiatrist. If he or she does not do talk therapy, ask for a referral to a mental health counselor who does. You need help to stop these distressing thoughts and get on with normal 16 year old life.
I wish you well.