Back pain and chest pain Need advice

So two days ago I got this ache in my upper left part of my back that also goes to the middle side of my back and I can also feel it in my chest which kind of hurts any thoughts of what it could be because I can’t be standing for a long time because it starts to ache more also I’m a 16 yr old girl

Also I’m having a hard time breathing like if my chest was filled with mucus or something 

Im a 16 year old female with the same exact pains lol. Mostly in my upper left chest like you said, & pain in the upper back. However i have thoracic kyphosis so that may be why. I also have GERD which causes chest pain as well. Get your symptoms evaluated. I suggest a chest xray first to see what it's looking like in there. Don't panic you'll be okay ❤.

How were you diagnosed with GERD? Also what does the chest pain feel like?

I should see a specialist to examine your spine just in case you have a trapped nerve causing the pain.