Breastmilk will start to increase after you give birth, say around 2-3 weeks the earliest. For me i dont drink lactation drink first and only started consuming supplements after i have given birth to increase my bm. After you have given birth you will start to produce colostrum first. So dont worry about your bm as of now. Enjoy your pregnancy journey!
It'll only start after birth. If you want to build a fridge/freezer supply then the more you empty your breasts, the more milk it makes. So if you want to produce more you need to feed, pump or express more often. But if you don't intend to build a supply then don't express/pump too often unless engorged or you can become an oversupplier.