Medication concerns

Katherine
I accidentally took a 60g Tefast tablet,which is an antihistamine, to help with my sinus symptoms but forgot to read the safety precautions first which said do not take during pregnancy or breastfeeding. It contains fexofenadine. Am really concerned this is bad for the baby. This is my first pregnancy, so still getting used to all the do's and don'ts. Am 8weeks pregnant.