Aortic Aneurysm Fear

about two months ago I started having chest pains along with back and left shoulder arm pain. I went to the ER 3 times because I thought I was going to die. They ran blood tests X-RAY and EKGs all came back fine and told me nothing is wrong with me and sent me home. Followed up with my physician and did an echo since I have some characteristics of someone who might have Marfan (tall skinny lanky long face) but echo came back fine. Now I sometimes have pains that radiate all the way from my left side to my left leg same thing from the base of my skull to my upper back. They can also feel like an electric shock or just regular pain. Also can visibly see my pulse through my stomach. Headache started two weeks ago and is constant. I am very doubtful it has to do with anxiety or stress as my life was not stressful at all when the pain started plus I took anxiety meds which didn't help to rule it out. Pain is constantly there mostly on my left side where the heart is and I am terrified it is an aneurysm since I don't think any of those tests would have caught that. I accepted it's not a heart issue as those tests would have caught that. I stopped working out completely as I am scared my "imaginary" aneurysm would burst if I raise my blood pressure or do any movements to aggrevate it. It is affecting every aspect of my life tremendously and I am lost don't know what to do anymore and feel like I'm going to die at any moment. Everything I go everything I do my chest and upper abdomen hurt nonstop. I even woke up several times in the first two weeks with shooting pain in my chest and down my left arm. I am convinced I have an aneurysm even though it was never diagnosed. Would appreciate any advice. What were your symptoms? How were you diagnosed?
I am 29 btw no high cholesterol active never smoked good weight/body fat.

One of the doctors said it might be costochondritis however I'm having shoulder, neck and arm pain I don't think it's a symptom of costochondritis. Plus it doesn't hurt when I breath in or sneeze. The pain is totally random. It does get a little better when I lie down and go to sleep, that's the only time.