Low milk supply

I really need advice on what to do to get my milk suppoly back up. For about a month now my daughter has started sleeping through the night but in doing so my supply has gone down. So when during the day when she eats every 2 to 3 hrs theres barely enough consistantly. Im going to start drinking tons of water and make sure I take my vitamins but what about in that window of time when she sleeps 8 to 9 hrs? Should I get up and pump (when I finally get to sleep) and if yes, how many times should I do it?I feel like I failed as a mother when my supply was barely non existing when I woke up this morning when usually they're engorged😭