Low milk supply

I have had to pump and feed since my baby was under 2 months old (she would not gain weight eating directly from the breast, even though she was feeding ever two hours for 30 to 45 minutes at a time) so my doctor wanted me to strictly bottle fed. Now that I’m only pumping I’m noticing my milk supply is low. I can usually only pump 3oz total or less (from both breast combine) each time. Now that my baby is getting older she is eating more per feeding and I cannot keep up. Does anyone have any suggestion to help increase my milk supply ? Has anyone tried milky mom brownies, I’m thinking about ordering but do not want to just throw money into things that do not work.