Chest pain when smoking or yelling (strange story)?

Back in September I was on two hits of powerfull hits of LSD. I was using nitrous oxide during the peek and started to pass out. As I was passin out what I saw terrified me and I began to hyperventilate way to quickly and aggressively so I really wasn't getting the oxygen then that I needed. I yelled as loud as I could just as i passed out and i felt the life get sucked out of me. But very little noise came out when I yelled. When I regained consciousness I had extreme pain my right side of my chest. I went to the hospital and got an X-ray and said they couldn't see anything and they told me the pain was probably imaginary. It's been 3 months and the pain is almost gone unless I yell or try to smoke weed. And when the pain starts the right side of my body starts to throb. What did I do to my lungs/chest. That's a short summary of what happened. I really want to able to smoke again buy it hurts to much. I typed this on my iPhone typos everywhere probably.

It's the nitrous. When you inhale uncontrolled doses of nitrous, you are basically causing yourself to nearly lose consciousness from oxygen deprivation. You may have slightly damaged your lungs also because nitrous in it's inhaled form the way most people do it (whipped cream cans) is very cold, colder than the air you usually breathe even in winter - that gets warmed by your respiratory system as you inhale, but people tend to suck down nitrous. This wouldn't show on an X-ray.
Since you damaged your lungs, I really wouldn't suggest smoking at all. And I definitely wouldn't suggest doing nitrous anymore. Also, do you find yourself short of breath or coughing a lot? You may have triggered asthma - also this will not show on an x-ray. I would suggest going to a doctor and telling him you "accidentally" inhaled some unknown chemicals one day and your chest has hurt ever since, and see what diagnosis you get.