Take the pre-reqs, if you had not taken them before. If you have, and you gave a dismal performance, then I recommend doing a masters, preferrably, a non-thesis rich in biomedical science, biology courses. The only pre-reqs you will need to RE-take, are those you made below a 'C'. Doing a masters will give you a new gpa for adcoms to consider and will stand out (granted you get a gpa >3.7) from your ugrad performance. Good luck.