Hi Evapman!
Question, when you vape do you hold the mouth piece infront of your teeth when you inhale? Think about it. When I first started thats what I did, I found that when I was inhaling I was holding the mouth piece under my lips (obviously) but infront of a single tooth on my left side, the canine tooth I believe. After about a week, that tooth began to hurt! I just posisitioned it behind my teeth and presto, no more pain. I think its not the acutal liquid that I was vaping but the warmth of the vapor that was causing pain...like when drinking a hot liquid. I don't believe that I have sensitive teeth, but after some time of "heating" your teeth/tooth it may affect it causing it pain. Heres a link to sensitive teeth for hot and cold.
When Heat and Cold Hurt Your Teeth Like I said I do'nt think I have "sensitive teeth" and maybe you don't eigther, but I think it could be linked to this issue none the less.
Note: If it happens when you lay in bed, could be linked to a sinus congested issue, or perhaps to the meds your on, as you stated. I'd take a look at sensitive teeth, then sinus congestion issues first.