Hello, Welcome to Healthcare Magic. In history you mentioned that, you had already evaluated by ER physicians and tests (hope they have ruled out cardiac illness too) are fine, then we should suspect anxiety or stress for cause of current symptoms. GERD usually respond promptly to omeprazole. Anxiety disorders can manifest not only with psychological symptoms but with a variety of physical symptoms also like: Tingling, numbness, hot and cold sensations, palpitation, chest heaviness, headache (like lightheaded in your case) choking sensation, tremors (shakiness) etc. Anxiety is more probable if these symptoms are present in your case. For long term control of anxiety following measures are helpful: relaxation exercise, medicines like SSRIs/Benzodiezepines and non drug treatment like CBT. Medical treatment you can take after consultation with psychiatrist. Wish you good health and all the best.