It's not anything to worry about, granted it terrified me when I found out I had it with my first baby. They will give you penicillin in an IV while you are in labor, if you are not allergic to it. I had a perfectly healthy baby naturally. You should be just fine :-)
It's a really common bacteria in people's bodies (about a quarter of people have it). Your baby 'catches' your vaginal flora (bacteria) during birth and it makes it's way into their stomach to begin their own gut microbiome (this sounds gross but is a good thing that kicks off digestion and immunity). It's just that very rarely, the strep b bacteria (more of a negative gut bacteria that thrives on processed carbs and sugars) can cause an infection in the baby. Doctors generally recommend antibiotics during labour as this reduces the chances even further. I am one of those weirdos who refuses the antibiotics because it also kills off a lot of beneficial bacteria and begins your babies health on a bad footing from the first minute. My midwife taught me how to monitor my baby 4 hourly instead so I could be quick to spot any signs of infection and give antibiotics straight away. I'm not against antibiotics as a treatment but I am against them as a preventative measure. Anyway, I weighed up the risks and that's what I chose... Most people are happy to let their doctor make the call though!
Group B strep (GBS) is a kind of bacteria that many people harbor in their intestinal tracts. The bacteria may also inhabit (or "colonize") your vagina as well, and be passed on to your baby during labor and birth. They will give you anti biotics during labor.