I am 14 weeks pregnant. I lost my previous pregnancy at 25weeks due to gbs sepsis. Now, a vaginal swab shows gbs+. My cervix is closed, ffn neg, but WBC 14, 200 (neutr 75%). I have no symptoms and am taking oral antibiotics. How likely is chorioamnionitis

Data not clear. A study done awhile ago showed that previous history of chorioamnionitis was not a risk factor for subsequent pregnancies, however I have other experts say that it is a risk factor. The bottom line, all you can do is follow doctor's instructions and stay as healthy as possible. Sleep, rest, a good immune system. Exercise, eating a good diet. Just try to take care of yourself as best as possible.
. If the previous baby had gbs sepsis this baby as soon after birth will need to be treated until cultures come negative. Also you will need to start on IV antibiotics while in labor. Atleast 4 hours prior to delivery. Discuss the plan with your OB and let the pediatrics know too. Gbs is a major problem during labor, while cervix is closed and you are not in labor you don' have a to do anything.
Unlikely. Chorioamnionitis will generally only occur if your membranes are ruptured.
Chorioamnionitis. You're definitely at a higher risk, but chorioamnionitis would happen only if there was premature rupture of membranes or if you've had ruptured membranes at term, are gbs + and not treated with antibiotics. In your case, it appears you went into premature labor at 25 weeks. This time, it's hard to predict chorioamnionitis since we're not sure if you go into premature labor again or not.