Accutane is designed for people with severe nodular and cystic acne that does not respond to other treatments. I'm quite sure that you do not fit in this category....you're probably using it to fend off steroid induced acne.
Which doesn't make any sense because there are topicals that can fight acne for those with moderate acne....such as tazorac or differin.
For people that have a need for this drug, 20mg per day would do hardly anything. When I was younger and taking accutane, 20mg per day would have done squat...I was taking much more than that with a docs prescription.
Accutane prescribing guidelines recommend 1-2mg per kg of bodyweight, with most doctors leaning more toward 1mg/kg.