Hello everyone! I have been having similar symptoms for almost a year and a half now, but I am still not diagnosed.

I’m a man, 28 years old. 170 cm, 55 kg. I have a chronic kidney disease (glomerulonephritis, stage 3). I control my blood pressure with Perindopril. Have never been overweight, but I’m not fit either.
In March 2021 I had a terrible headache, chest pain, higher blood pressure than usual, difficulty focusing my eyesight (for example, I couldn’t read), dizziness. This episode lasted for a couple days, and ever since it went away, I had these symptoms:
• Constant chest tightness and chest discomfort, primarily on the left side. It feels like something is squeezing my chest.
• Constant shortness of breath and inability to take a satisfying breath. Feeling that something in the chest doesn’t open up and air doesn’t reach where it is supposed to go. Breathing feels shallow. I cannot breathe in enough air even to talk and I get out of breath when speaking all the time.
• Very frequent, almost constant, chest pain. The pain is usually right under my left breast, where I can feel the heartbeat. It feels like intense squeezing or pressure. It can sometimes radiate to left shoulder blade. I wake up with this pain in the morning quite often. I can’t seem to pinpoint what triggers it. The pain doesn’t necessarily come during or right after light training that I do (although that can happen, too).
• Palpitations, not very frequent
• Strong heartbeat, feeling of pulsation in the body (especially after a meal)
• Dizziness, brain fog
I experience chest tightness and difficulty breathing literally *all the time*, they never subside. Chest pains come and go.
At this point I have done these tests, some of them multiple times:
• Blood and urine test: don’t show anything except for my kidney disease
• Spirometry: shows slight reduction in lungs volume. Asthma medicines give no improvements.
• Chest X-rays
• Electrocardiography
• Echocardiogram
• 24-hour Holter monitoring
• Heart CT scan: showed an insignificant atherosclerosis, my doctor says it shouldn’t give symptoms like these. Same was found in my neck arteries (with the help of ultrasound).
• Gastroscopy: esophagus is fine, but I have erythematous gastroduodenopathy. Not quite sure what that is, but I was told it was nothing to worry about.
I have used three different asthma inhalers for half a year without any effect. After CT scan detected this slight atherosclerosis, I started taking Atorvastatin.
I don’t hyperventilate. I breathe at a normal rate, but always feel air hunger. Periodically I kind of force myself to take a deeper breath. It can be successful (and I feel that my chest opened up properly and air went where it was supposed to go), or it feels like my chest doesn’t increase in volume after specific point and I don’t get a satisfying breath. The same with yawning. Sometimes it feels like something opens up in my throath and chest, but more often that doesn't happen and yawns feel incomplete and unsatisfying. Oximeter shows normal oxygen saturation of the blood (even during light training).
Some doctors I’ve encountered suggest that this is psychosomatic, but doubt it because a) I’ve never experienced any panic attacks or similar, and b) it doesn’t explain the starting episode.
I am vaccinated against corona.
All in all, doctors claim my heart is ok. Asthma medicines don’t help. Majority of the symptoms are there 24/7, without changing much for better or worse . I have been to ER a bunch of times, and my doctors have no idea what this could be.
Is there anything else I could/should do to check my heart or lungs? I have done multiple heart tests, and my doctors say that my heart is ok. How sure can I be about it? Considering the discomfort and pain in the left side of chest, I can't help thinking that this is heart-related. On the other hand, after this much testing they shoud have found something, if there were any pathology.
I also get heartburn quite often, it’s uncomfortable, but not too bad. Can one have GERD with healthy-looking esophagus? I have been taking famotidine for two weeks (10mg in the morning and in the evening), and it helped with heartburn, but it didn't give any relieve from other symptoms. I'm trying pantoprazole now. If it doesn't work either, should I go on and try prescription GERD medicines?