I have lower back pain kind of like constant stabs?!

I have lower back pain kind of like constant stabs?

I was bending down (legs straight) and I just fell down because of the pain. It was like someone was stabbing me in the lower back.

I went to the doctor and he said it's because I'm still developing (I'm almost 17). I don't trust this doctor because he wrongly diagnosed a cold when I actually had pleurisy and pneumonia. I can't go to a different doctor so help me out!

maybe it is your kidneys. mine used to give me bad pains when I consumed too much caffeine. drink lots of water. and maybe get another doctor when you can.