R.S.
I had to take a class c drug during both my entire pregnancies. Both my children are healthy...no birth defects, etc.
I did my research and on my particular drug it increased the chances of cleft palate. But the percentage that it increased it wasn't enough for me to worry over much.
Research the drug and see what the known effects are on the baby...and like drinking alcohol before finding out you are pregnant there is a window when the baby is not yet attached to your uterus and so it will not be effected by drugs or alcohol.
Try and think positive until you see your doctor and just don't take anymore until you find out what is the right thing to do from a medical professional. Sending you a huge hug!!