Increase breast milk

My milk supply from 100ML drop to 50ML to 20ML. When i use breast pump to pump always nothing come out, so i have been using hand to pump out. Is there anyway to increase my breast milk? Tried eating oats, avacado etc but don’t seems to help at all. Felt so frustrated that my milk supply become lesser and lesser. Felt so bad that i can’t give my baby breast milk.