An SMP is a last-ditch, no-options-remain effort. In your shoes, yes, you should be looking at doing more undergrad study, at least to get your cumulative overall and science GPAs up over 3.0.
But do the math here: you literally CAN'T get up to a 3.5 from a 2.7, if you're interested in MD schools. Even four more years at a 4.0 will only get you to a 3.4 or so. Only DO schools "forgive" repeated coursework, and they still get to see your transcripts.
Best of luck to you.