Are you lactose intolerant? I am, it took me 10 years to figure out. The symptoms started when I was in my late teens. I figured it out when I was 30 after many years of pain and discomfort. My doctors could not figure it out. I noted that it was really bad after eating cereal. Then one day I saw a commercial for Lactaid milk and the light bulb went on.
I don't go near dairy, except cheese. I can tolerate cheese because the enzymes that make cheese convert the lactose to something I can digest. The abdominal symptoms went away for me.
When the undigested lactose in dairy hits your lower intestine copious amounts of gas are produced as the bacteria flora there will ferment the lactose. It produces carbon dioxide, methane, and hydrogen. This is what causes the abdominal symptoms.
Also, being vegetarian may lead to deficiencies in certain requirements such as amino acids that regulate muscle control, do you supplement to help with this?
Your stomach can definitely be affecting your heart. The vagus nerve gets irritated and sends signals to the heart causing it to act up. You may want to try antacids when you eat to help alleviate the palpitations. But I do believe antacids may cause your magnesium levels to go low so you will want to have them checked if you take antacids for the long term. But yes, your stomach can be part of the problem. I always get pvcs after I eat for about an hour or so but they tend to lessen if I take the antacids before I eat. As for the dreams I kind of think they are an expression of your desire to get the heart issues out of you, fixed and cured. Obviously your heart issues are top of mind and your subconscious is doing its best to try to figure out how to deal with them. In any event, your heart is likely in fine shape even with the palpitations but if you haven't been to a cardiologist you may want to get a check up just for your peace of mind. The gloopy feeling is likely transient and only related to the palpitations but get a baseline evaluation of your heart is always a good idea if you are experiencing symptoms. Take care.