Milk supply

I had tried to pump every 3hrs daily for 3 mths with taking all kind of milk booster ( fenugreek , legendary milk, mama choice drink , lactation cookie , madam patrum…) however non worked for me so far and my supply only around 700 ML which dropping again. Just wondering if any mum similar like me have other option to boost milk( i also did power pump 20 mins pump- with 10 rest / pump but also no effect.)