Hi, 26 year old male here....

I'll provide a bit of background first; Up until around 2 years ago, I was relatively healthy and not an anxious person at all. At the time, I was doing high intensity workouts 4 or 5 times a week plus playing football and running. My problems seemed to start following a game of football. I think I overdid it in the heat and when I stopped playing, my vision was all blurry and I had a migrane for the rest of the day. In the weeks that followed, I started getting heart palpitations on a daily basis. This caused me to worry and I went to get them checked out. After numerous tests, I was given the all clear.

Following many ups and downs over the past couple of years, all the panic attacks, trips to A&E (Nothing has ever been wrong) and feeling like I have experienced every symptom under the sun! This is where I am now:

Common symptoms:
Shortness of breath - By far the worst symptom I have. I've had this to some degree every day for around a year. Some days are worse than others.
Fatigue - Again, some days are worse than others but especially lately I've been feeling more fatigued
Palpitations - Improved greatly since I started taking Magnesium citrate but still get them ocassionally
Weakness feeling (Not as strong or frequent as the other symptoms)
Light headedness
Head feeling fuzzy

Tests I've had completed:

ECGs (Many!)
48 hour ECG
Echo
Chest X-Ray
Peak flow (Twice)
Oxygen levels
Full round of blood tests

All tests/checks have been fine apart from a raised level of Bilirubin, which has increased on both of my last 2 blood tests and is now at 38. However, the doctors dont seem too concerned about this.

It might seem strange, but despite me being anxious about my symptoms and experiencing panic attacks sometimes, I can still be a rational person. I can see how my anxiety makes my symptoms worse. I can tell how my breathing and the other symptoms get worse when I am out in public or at work but ease when I am completely relaxed and doing breathing exercises. However, I just feel that they never go away completely. I have gone from being able to run 10k or run around at football for 2 hours and feel fine to a point where on my worst days, I don't want to walk anywhere in case my breathing feels worse. I don't feel unfit, I have been that before when I was about 6 stone heavier. This feels like different.
My doc prescribed me Citalopram but it made me 10x worse so I stopped after 3 days.

I think what I am getting at is that I understand my symptoms can be caused by anxiety but I'm thinking there might be something else I can check for or something else I can try. Does anybody have any advice or anything that has helped them with similar symptoms?