Well, it might still be possible to get into nursing school. Your GPA is only one factor. However, a couple of suggestions:
1. You can take some additional science type courses like epidemiology or immunology, nutrition, etc., to raise your GPA.
2. Point out in your essay that your GPA has increased now and bust your butt to get an A in microbiology.
3. If you got a B- or worse in any prereqs then you could try retaking those.
4. Make yourself a more interesting candidate by volunteer work, Peace Corps, AmeriCorps, etc.
5. Don't rule out private colleges. They can be more flexible with admissions and often have their own scholarships
. There are also a lot of loan repayment or forgiveness programs for nurses.