Feeding issues

Hello mummies, my baby is turning 11weeks old soon. I find that he takes very long to drink his milk (1hour), doesn’t show interest in drinking. Currently I’m feeding him 120-140ml. Should we actually be feeding on demand? Cause I also find that sometimes he sleeps a lot and don’t really cry for milk. So that’s why we are doing 3 hours interval, but maybe that’s why he is not hungry? If we feed on demand, what if it has been more than 5hours and he don’t make any noise? Please help.#pleasehelp #FTM #firstbaby