Please get to a hospital. They can give you medicine that will help with the detox symptoms. Some people get tachycardia when they stop drinking alcohol. Please get help.
I fou d exercise, stretching, iced tea, Epsom salt baths, and deep breathing techniques very useful. Depending how long you've been dependent on a substance it might be safer to speak with someone about a medical detox program to get you through the worst part. Good luck stick with it and keep a positive attitude and you will get through this.
I agree with the suggestions above. I want to say I'm proud you are journaling your experience; it's therapeutic for the writer, listener, and reader. On my two detoxes, I sought professional help. I don't know your financial situation, I encourage you to seek a social worker to explore options. You'll be amazed at all the options you have available in recovery. You don't have to go thru this alone. This too shall pass.
Are you medicated for anxiety? It could just be anxiety. My anxiety exhibits that way, plus my throat tightens up and I start gagging.
Edit to add that you may want to research Grounding Techniques. That made all the difference for me.
I usually distract my nervous system, take a dunk in an unheated swimming pool or take a cold shower.