I have just found out i'm pregnant, but have been taking effergin for weeks, will this have harmed the baby ?

Unlikely but stop : Nutritional supplements like this one do not have fda supervision and not enough studies have been done to demonstrate safety for a fetus. It is not likely that any harm has been done but go ahead and stop using it now.

You can't go back : Congratulations on your pregnancy! it is impossible to know but the chance of significant harm is low with ephedrine (ephedrine sulfate). Whatever done is done--you can't go back. I would stop all those now and start taking prenatal vitamins, eat healthy, exercise regularly, don't smoke/do drugs, and course consult your doc/ob physician for evaluation and plan for the remainder of your pregnancy. Best of luck to you.