Could definitely be the nicotine from what I've read. I'm on Prevacid for reflux (Diagnosed with Barrett's esophagus) and the meds worked perfectly until I switched to vaping about two weeks ago. Now I'm getting a little bit of heartburn/reflux, but it seems to be getting better over time. Honestly I think some of us are getting more nicotine than we did when we smoked- and I'm ok with that; it's better than tar & carcinogens.
That said, go see a doctor. Don't mess around with chest pain. Even if it is just mild heartburn- there are a lot of great options to treat it so it doesn't progress to something worse.