Well, basically the T can go eff herself at this point.
Zoloft is a preferred drug for breastfeeding and has long been that (for at least 15 years). So you are on a drug that helps you, that does not produce much untoward action for the fetus, and that will allow you to nurse your twins. So rejoice - the situation could be much worse.
Sertraline (Zoloft) use while Breastfeeding