Pumping, breastfeeding, Supply?

Sandy
Hi All! My Twins latch on for about 10 minutes and bottle feed (with breast milk) to get full. So I'm latching them on and also pumping every 3- 4 hours. My issue is that with all of the latching, pumping, lactation cookies, teas, fenugreek and drinking LOT of water I feel as though my supply is not increasing! I only have enough milk in my fridge to make it through their next bottle feed, but never more. How do I make more milk? Please help! I'm so tired of it all and ready to give up and switch to formula