Dear mellymells:
Yes, you can buy prenatal vitamins over the counter without prescription. Do make sure that it is from a reputable manufacture. You can ask your local pharmacist for over the counter products.
I'd also recommend for you to have regular follow-up visit with your primary care provider.
Good luck!
For more information on pregnancy, please go to:
1. Pregnancy - Medline Plus
http://www.nlm.nih.gov/medlineplus/pregnancy.html
2. Nutrition During Pregnancy - The American College of Obstetricians and Gynecologists
http://www.acog.org/~/media/For%20Patients/faq001.pdf?dmc=1&ts=20131216T0042456062