Constant upper back pain-pressure between shoulder blades. X-ray shows spine’s OK. What is it??

Patient: I’m 26 years old. I usually sleep about 5 hours a night. I’m also a heavy smoker and overweight. I have suspected GERD, and I take omeprazole 20 mg for it.Been having constant dull pain between the shoulder blades in the upper to mid back for about 2 weeks. There’s a feeling of heaviness or pressure on the spot when it isn’t hurting. Its accompanied by a feeling of uneasiness in the chest, and shoulder aches. Also my left forearm tends to ache a lot.I went to hospital several times but seems the doctors don’t know what it is. As an English speaker working in a non-English speaking country, communication is definitely an issue when visiting the hospital.I received medicines for cold, viral respiratory infection, irritable bowel syndrome, muscle relaxer and asthma, and still no change. X-rays were done of my spine on Friday, but apparently all’s well according to the orthopaedic.I had a CAT scan a year ago when I had another problem with chest pains but they found no obstruction of the aorta. After that I was told I might have GERD and have been taking omeprazole since. Haven’t had any checks since then.I’m fearing it could be my heart as the pain worsens at night, and when at work. I’ve already taken several days off to go to the hospital.I want to know what the possible causes of the pain are, and whether it is urgent enough to request further tests of the heart, gallbladder or respiratory system??