So what do you do?

I think this was discussed elsewhere, but I really have no idea why providers are reluctant to give the Hep B vaccine to parturients- My guess is ignorance, but I will withhold judgement until I actually talk to these "providers".
CDC recommendation from the website (http://www.cdc.gov/NCIDOD/DISEASES/HEPATITIS/b/faqb.htm ):

"Can hepatitis B vaccine be given during pregnancy or lactation?
Yes. Hepatitis B vaccine contains no live virus, so neither pregnancy nor lactation should be considered a contraindication to vaccination of women. On the basis of limited experience, there is no apparent risk of adverse effects to developing fetuses when hepatitis B vaccine is administered to pregnant women. Meanwhile, new HBV infection in a pregnant woman might result in severe disease for the mother and chronic infection for the newborn."

As you are a future nurse, please start to educate yourself and those around you as to the facts- never take anyone's word on anything- verify it yourself. You will find that many decisions in healthcare are not based in evidence, but in "common practice" and "CYA" that are not in the best interest of the patients.
Having worked NICU and having to take care of Hep B babies- Please get vaccinated!!!

If you are concerned about teratogenesis, wait for the 3rd trimester to start just to give you peace of mind.
If you go the titer route and are negative, then print out the CDC recommendations and ask exactly why you can't have the series. I think you will be surprised at the response.