Pepcid and omeprazole both reduce the production of stomach acid, omeprazole much more so than Pepcid, which is an older generation drug. They both come in two week packages, with warnings not to take beyond those two weeks without seeing a doctor. If you try them and see relief, then that would point toward reflux as causing, or at least contributing, to your problems. If they don't do anything, then you probably need to look elsewhere (unless you have laryngopharyngeal reflux, also known as silent reflux. But the symptoms for that usually are hoarseness, shortness of breath, postnasal drip, ears/balance being off. You could ask about hiatal hernia. Sliding hernias may not show up on an x-ray if they have slid into place at the time of the test. When they slide into the chest cavity it causes chest pain. Someone else brought up gas as a possibility. You could try the low FODMAP diet for two weeks and see if that improves anything.

The liver is under the chest. I would think a PCP would start with a full blood panel and full metabolic panel to see if that gives clues. Common cardiac tests are EKG, echocardiogram, stress test.

There are probably half a dozen likely possibilities to run down. If you feel stressed try breathing exercises or meditation and see if that makes a difference. Do you use white noise while sleeping? I leave the TV on for the noise background but wear an eye mask to avoid the light. If you don't do anything like that give it a try, you can get white noise on free apps. Again it might help you get more info while awaiting an appointment with doctor. The other thing is to post in the heart section of Mayo Connects.