I'm very sorry for your current predicament. This whole process can be very taxing and disheartening. While I don't have alternative career plans, per say, I have plans to improve my credentials if things don't work out this year.
I'm not sure what your particular situation is, but if there's one thing I can tell you, it would be to not give up. As a first time applicant, I can't necessarily relate to what you're going through, but I think it's important to take a step back and look at how far you've come. Honestly, you should be proud of your accomplishments, as so much as even applying to medical school is a huge accomplishment in itself, let alone pursuing a masters degree in biology.
If medical school is what you truly want, then don't let that dream go. I believe that hard work and persistence pays off. At this point, I think you need to look within yourself for motivation and strength to do everything you can to give yourself the best possible chance for acceptance somewhere. After all of your hard work, you at least owe that to yourself. Send updates to schools that allow them; inquire about your application credentials at schools to which you've been rejected; maintain good grades in your MS program; find out if there's a red flag hindering your application; consider looking into a program like StudyShy mentioned, as a handful of schools offer such programs; etc. This is all under the assumption that medical school is what you want, and if that's still the case, I can't really justify recommending alternative careers. If you're having second thoughts due to a change in personal interests, then that's obviously a different story.
I hope things work out for you and I sincerely wish you the best of luck!