Shortness of breath..?

I'm such a hypochondriac... this is the second question i've asked on breathing... Anyway, for about 2 to 4 weeks(i don't quite remember exactly when it started) i have been experiencing an extreme tightness in throat and chest and shortness of breath for the whole 2 to 4 weeks straight. note i have bad anxiety/depression. my doctor said it was because of anxiety.. but it just doesnt feel like anxiety. and lately i have been trying to drink alot of water and i end up urinating every 15 minutes! that doesnt seem natural. i've had alot of gas problems too. i don't know if those are related to anxiety.. but looking up those symptoms on the internet do not help. it says those are symptoms of possible kidney failure.. i'm just worried as hell. i'm 18, i'm too young to feel like i have a serious problem. please someone help. thank you