Can someone help me understand this?

I've wanted to seek help for this for a really long time but have felt embarassed and uncomfortable trying to speak about it.
I decided to try posting something here to see if anyone had any answers for me.
 
Ever since I was really young, I've had a really bizarre response to sex and sexual situations.  Even just sexual jokes.  I get a wave of heart pain, similar to when I'm stressed or anxious.
I figured I was just one of those kids that was a bit shy about sex and such, but even now that I'm 17 and surrounded by sexually active friends, nothing has changed. 
 It's just gotten worse.
The other day a male friend winked at me jokingly, after I accidentally said something that could be taken the wrong way.  I nearly instinctively grabbed my chest from the burst of heart pain.
 
Even just light jokes about sex, or people telling stories about things they've done, I find myself in pain, my heart rate goes up and sometimes I find myself short of breath.
But it's not even just that.  I react that way to my own body.  The other day I noticed my shirt was so thin I could see through it.  The sight of my own chest caused me pain.  The other day I ran up stairs without a bra and held my chest and even that caused pain.
 
I don't understand what it means.  I've never had sex and while I'm not exactly launching myself at people, I'm not afraid of sex either.
 
I've tried looking this up online, the closest thing I've found so far is Sexual Aversion Disorder.  But nothing is mentioned about heart pain.
 
Please can someone help me understand.