You haven't told us the most important piece of information - do you have enough data for your work to be publishable, or are you just being impatient? If your project is stalling, my bet is that your PI hasn't brought up publication because your project isn't ready for that yet.
Reality check: you may not publish anything during your undergraduate career. That's OK. Research takes awhile and MD/PhD programs understand that. I had no pubs from my undergraduate research (just a few posters/presentations) and that didn't hurt me at all during the application/interview process. In all honesty, if you're putting in less than 20 hours/week, I wouldn't expect you to have publishable data after just a couple of years unless you're doing clinical research, bioinformatics, or something else that moves a bit faster than basic science research. If your mentor is head of the MD/PhD committee, my best guess is that you're in a solid lab with good mentorship and that you need to adjust your expectations a bit. Instead of thinking about publishing right now, think about why your project is stalling and ask your PI about that. You can also ask about local conferences that may give you a chance to practice presenting your research. You can always make things better...but I don't think switching labs is the best way to do that in your case.