boost milk supply

my supply dropped drastically due to not pumping regularly.. I try to pump every 3h to only get 60-80ml, btw I dont latch on as i can't get lo to latch properly so I'm exclusively pumping only. the only time I can get 150-220ml is pumping after 7hours> my MIL suggest i eat more fish to boost supply. would like to know are there any more food/soup to boost supply