has anyone taken meds to start a period?

I've got an appointment with a dr this afternoon, I'd just like to hear people experiences, good and bad. my last period was 3 months ago, I only found out in January if you go longer than 12 weeks without a period it can cause damage inside your body, I've never had regular periods and the longest I've gone without was 13mths. this is the first time I've taken meds but I really don't know what to expect. any help or advice to calm my nerves?