Ellmila, welcome to the forum.
First check out information in the general allergy posts - the ones at the top of the list of threads.
If you put a couple of keywords (sulfite allergy, sulphites, sulfite sensitivity, food journal, challenge testing .... ) into the search box at the top of the page you will find a whole bunch of links to posts.
There are lots of links to good websites in the older posts.
Since you reported chest pain, it's always good to get checked out by a cardiologist, just to make sure there is nothing going on with the heart. My stomach and esophagus symptoms cause real heart arrhythmias (linked angina or cardioesophageal relfex). It caused my coronary arteries to spasm, which ended up as a heart attack requiring a stent at that spot. My cardiologist still doesn't believe me, but I can reproduce the reaction just by drinking a glass of wine.
A gastro doc is unlikely to be conversant with sulfite intolerances. I even had to go to 2 allergists to find one who put me onto keeping a journal. The first one did a couple of skin pricks and told me I didn't have any food allergies.