Lower Back pain in teenagers?

I'm 14, and I've had severe back pain and spasms for 6 months now. I do not play competitive sports, mainly because of my asthma, and I swim a lot. Im not unfit, but not really fit either. The pain never goes away, and I cant do stuff I used to be able to do anymore. I really need some help! My Dad has the same problems, and he has narcotic pain medication to take regularly, do I need something stronger than ibrofen? The doc wont do anything at all because 'it's not normal for teenagers to have bad backs, stop faking!' I feel this is really unfair, as I can barely move! I have GCSE's coming up, D of E walks, and I'm going to NYC in a few weeks! I really want to get better! Please help me!!!