Milk supply... Pls help

My milk supply decreased. Only this past weekend i was leaking milk. Now, for the past 3 days not even a drop. I put baby to breastfeed and he cries because i assume there is nothing coming out. I want to breastfeed till at least 4-5 months. But it seems i have no supply. How can i increase it? Pls help i am desperate. Thank you