I have group b strep i'm 33 weeks pregnant and allergic to penicillin? any advice

Clindamycin: Clindamycin may be used instead. Also, cephalosporines such as cefazolin seem to be indicated as well. Cephalosporines and penicillins may cross react occasionally, so depends on what your penicillin allergy is that your doc will have a chance to decide what the best choice is.

Erythromycin .: Unlike central nervous system syphilis, there are other antibiotics for beta strep (i presume you meant a throat infection). After you have delivered your baby, you should contact an allergist to get you tested to penicillin since most people tend to lose their penicillin allergy after a few years.

Different antibiotic: Your OB will likely prescribe a different antibiotic to treat the strep during delivery. However, most people labeled as "penicillin allergic" do not actually react to penicillin. Among those with a genuine allergy, ~80% will lose their allergy after about 10 years with no exposure to the drug. Consider seeing an allergist, as they can perform tests to see if you are currently allergic.