Back in high school, this thing happened where I started feeling this sudden pain in the left side of my chest. It was only a mild ache most of the time, but then, there were these sudden bursts of pain where I couldn't help but clutch my chest and almost felt like I couldn't stand. As you can imagine, this kind of freaked me out -- I was worried I was about to have a heart attack or something. @_@
Turns out, though, that it was just costochondritis -- which is caused by inflammation of the cartilage in the rib cage. Nothing to do with the heart (reassuringly). What was weird about it, though, was that no one was really sure how I got it. It's a fairly common sports injury, I was told, but, I don't play any sports. @_@ Best hypothesis my doctor had was that my backpack was too heavy. Also, what's weird about the condition in general is that it apparently usually only affects the left side of the chest, which is... weird. >.< Unsurprisingly, this leads to a lot of people getting it and then worrying that they have some sort of heart problem... Anyway, though, they told me it was nothing to worry about, really, just some pain that would go away after a few months. Most of the time, it was more annoying than anything else.
Only trouble was I had to keep reminding my friends not to hug me, since any pressure on that area would make the pain much worse. I had a lot of hug-y friends at the time, and, normally I didn't at all mind them hugging me, but, in this case, yeah... DX Hell, sometimes I would even forget -- which was especially problematic given the fact that, before this, I was so comfortable with them hugging me that they didn't even need to ask. So, if I wasn't thinking about it, they'd come in for a hug and I wouldn't really try to stop them and then suddenly pain. >.<
Worst part was this one day when I was wearing, uh... a cat bell (don't ask). Point is, there was a round piece of metal strung around my neck and basically sitting on top of the spot where the pain was the worst. So then another one of those hug things happened, therefore pressing the bell into my chest and, yeah... >.< I screamed and practically pushed my friend away from me, then slowly sunk down to the floor, where I curled up in a ball for a minute or two until the pain subsided. >.<
Thankfully, though, when it wasn't being bothered like that, the pain was so dull most of the time that it was hardly even noticeable -- except for those occasional bursts where it would just... hurt all of a sudden, for no clear reason. And those were the moments where I had to remind my friends that, if they saw me suddenly clutching my chest in pain and steeling myself against a wall or table to keep myself upright, that there was nothing to worry about and that I was fiiiiine even though I clearly didn't look like it... XD