If i were you id seek an answer from a different dr, no pain is normal pain, pain signifies that something is wrong. Did they run any tests on you or anything? Or just pretty much look you over and that was that? I would definately ask for a 2nd opinion on that.

Go to the E.R. and request an I.V.P. They will shoot dye into your blood stream and x-rax your kidneys,bladder, etc. If you have any blockage or stones they will show up. I have had kidney stones twice now and both times my testicle ached on the side it was on before I had back pain. Get it looked at-may be too big to pass and they will have to break it up (if it is a kidney stone). Let me know what you find out...

Despite your age that practically young, which uncommon to get troubled by kidney stones, your lower back pain reminds me with one of common symptom the presence of kidney stone, there for you really need to start watching it closely, is this symptoms also follow with other signal, like obstruction in urinating, acute pain in the lower abdomen and groin, fever, nausea and vomiting or even the presence of blood in the urine. And is this symptom just come and go or become regular symptoms.

But of course you still need consult to your doctor and make some proper test to make sure your problem.

Blessing

might be a stone.did they xray you? take urine test ,blood test?
sounds like a kidney stone.or maybe prostate problems.however im no doctor.hope you can find one to check you out well.