Several questions here.
1.) When did you apply? Did you submit your AMCAS in June, or did wait until August? Later app= worse chances
2.) Where did you apply to? Only top 50- you've lowered your chances significantly. Did you pick schools with a high in-state preference? Did you apply to your state school? Did you pick the right schools for you- for example, did you apply to schools with a heavy emphasis on research (90% applicants have research experience) and you lack significant research? The MSAR provides details on the percent of applicants applying to each school with clinical, non-clinical, and research experiences.
3.) What do your ECs look like? Do you have clinical experiences? Non- clinical volunteer work? Research? A hobby? I think most applicants need a combo of at least some of these to be successful.
4.) What did your PS look like? Did you have other people read it over to give you feedback on it?
5.) What were your LORs like? Were they from people you know well, or just some professors you spoke with once or twice?
6.) What were your secondaries essays like? Did you answer questions on why you want to attend the schools thoroughly? Proofread each answer?
These are a few points you might want to look into. As a reapplicant, I can fully sympathize with what you're going through right now, and I can assure you, your lack of interviews is not due your lack of 'smarts' or 'fitness.' There's something the matter with your app, and most likely, something that can be remedied.
Be careful with looking into other programs, like dentistry and pharmacy. If you are truly interested in them, go for it, but if you want a back-up in case your med school app falls through, you're going to be in trouble. Just applying to med school is exhausting physically, emotionally and financially, and attempting to study for the DAT, PCAT, and fill in those applications while simultaneously applying to med school will lead to sub-par, slapdash applications all around. You will waste large amounts of energy and money doing this, when you could be improving your med school app only.
4.)