I agree with Kuve S, there isn't anything wrong with having both a Mistress and submissive as long as both parties are well aware of everything going into the relationship.
Also, its best to be honest with yourself and what you are looking for that way when you do go out searching for either a submissive or a Mistress you will have an idea of what you are looking for at that time. I will also suggest getting some reading material also, maybe trying to find a local group or a group that you feel comfortable with to discuss some of these issues/concerns you are having because you are not alone!