A 3.7 GPA is low for MD/PhD programs, which typically have GPAs in the 3.8+ range. (Many are 3.9+)
For a MD/PhD, you’ll need a higher MCAT too. A 515 or above. .
See [MCAT Scores and GPAs for MD-PhD Applicants and Matriculants to U.S. Medical Schools, 2017-2018 through 2018-2019
2018](https://www.aamc.org/download/321548/data/factstableb10.pdf)
Being under 18 is a severe handicap for med school admission. Probably a bigger barrier than your GPA.
Being under 18 will also make it difficult to impossible to find clinical experiences due to HIPAA and insurance issues. You’ll have much better luck once you turn 18.
If you have a strong research profile and the support of your PI, consider applying for some NIH summer scholar programs next year. AMGEN is specifically designed for future PhDs and MD/PhDs and is typically done during the summer between their junior & senior years.
AMGEN-- https://amgenscholars.com
https://www.training.nih.gov/amgenscholars
Don’t earn graduate degree. It won’t enhance your chances for medical school. (Grad GPAs are pretty much ignored by adcomms, unless they’re bad–then it will harm your chances.)
RE: Gap year
It’s now the norm to take a gap year or two between undergrad and med schools (60%+ of matriculants have gap years) but…
for a MD/PhD hopeful, a gap year could be harmful if you are away from the research environment. (Your knowledge & skills get stale.) But unless you have everything else in order–your pre-med ECs, LORs–as well as your research resumé, applying to med school directly from undergrad will be a waste of time & money.
For your gap year consider applying for positions as full time research assistant or research lab manager. You will be hands-on and may have the opportunity to enhance your research CV with a publication.
G-SOAR is a 1 year full time research internship at NIH for new BA/BS graduates.
G-SOAR—https://www.training.nih.gov/gsoar_home_page
Similar positions are also available at all major academic hospitals, state and federal research institutions, and private biomedical research institutions.