Low supply

I am trying everything to get my supply back up. I am 9 weeks PP and got my period last Thursday (8 was pp). Ever since my supply has dipped really really low. I pump every 2 hours (back at work so that’s as often as i can) for about 15-20-25 mins. The flow typically stops after 7-8 mins. I’m only getting about 2 oz total every time. I drink tons of water (about 100 oz/day) and just started trying to eat a combination of oatmeal/flaxseed/brewers yeast 2/day. I have ordered supplements (Liquid Gold from Legendairy Mama). I haven’t seen any change in my supply since doing these things. Is there anything else I haven’t tried? Could it be my birth control? I’m on the mini pill for breastfeeding moms.