How soon before your pregnancy is the first question?  Also have you been pregnant before?  And a doctor would want to know about meds?  Don't feel embarassed to ask your doctor.  Since you allude to being pregnant I am assuming you are seeing one (or if the baby is here you are still seeing one).  Usually the lactation is hormonal when tied to an acutal pregnancy but can be brought on by a false pregnancy. 

 Best to speak with your doctor...