shortness of breath and chest pressure!!

PLEASE HELP.
I'm 15 years old and I've been healthy all my life. Up until about 3-4 months ago, I started getting bad shortness of breath. Like I'm constantly short of breath. I get chest pressure too. I dont think its a heart problem because I feel like its in my lungs. As if my lungs cant expand right and that it's mainly in my right lung. Sometimes I get these sharp pain on either side of my chest but I feel like they're in my lungs. Sometimes my shoulders hurt and I just dont know what to do anymore. I had a chest xray and it came back clear so my doc just thinks its anxiety. I really dont think it is. Helpp!

[harkinz]

i forgot to say, the months before that, i would get shortness of breath just going up the stairs and im not overweight!

[raju208]

hellow first varfy it is an major problem or not and also it can the normal problems which occurs in tenn agers slepp on plain surface and take large breath for 5 times then also u get the than to a different doctor and if u r boy do u have pain whn ur chest nipples just pressed because i am telling it is normal in tenn agers