It is not very clear from your mail whether there is an acute infection (active infection) or just a positive HBsAg. As HBsAg screening is being done routinely nowadays, we are detecting it in people with no symptoms at all. If you have no obvious symptoms you could just be a carrier without having an acute asymptomatic disease. To differentiate between the two (as the two have different prognosis). If you are found to be positive on routine testing, a liver function test and HBeAb and HBeAg are essential at this stage. (HBcAb and HBcAg are not required as they are unhelpful).
If you have acute hepatic infection, you have to be under the care of a gastroenterologist / perinatal physician as most general ObGyn physicians are unlikely to know much about it. Not much in form of treatment is to be given even if you have acute infection but special care is required - general care and nutrition, as prognosis of acute infection is worse in pregnancy than in a non-pregnant person. So, you will require further care only if you have an acute infection and you need not bother if you are a carrier.
The risk of transmission to the fetus is there and nothing much can be done at this stage to prevent it. Once the baby is born an expert neonataologist will check the baby to exclude HB positivity and once the baby is negative for HB he / she will give the baby immunoglobulins and specific HB vaccine which ensures 90% protection if used within hours/ days of delivery. Those not covered by it are assumed to have had an intrauterine infection. The concern of passing the infection to the infant is genuine and you need to deliver in a good centre with expert neonatal care available round the clock or bring the baby to a special neonatal unit hours after delivery for testing and follow up action.