Your chances are very slim. Although we do a few here in their 20's & 30's, the majority are in their 50's. Living in fear is never a good thing though and you should find out what the source of your pain is. An ENT would be better than a dentist if you want to be sure (see your family doctor first and get a referal to an ENT if he thinks you need to). Pain can be a symptom of many things besides cancer, in fact, many of who had cancer had no no pain (I for one). I just had a golf ball+ size tumor in my throat that was highly visible and when I asked my dentist what it was, he couldn't tell me. My only other symptoms were a little raspiness and a feeling that something was stuck in my throat.

I am sorry that you have to be exposed to second hand smoke. I am a musician and was exposed to a lot of second hand smoke before smoking was banned here in California - it might have played a role in my cancer, but typically it takes many years of exposure. Just avoid it as much as you can.