Pumping enough milk

I always have this worry that I might not be able to express enough milk for Baby. Currently she latches on so she has enough. But when I express milk out, I usually get about 120-140ml in the morning. Thereafter, always left than 50ml.

I've just received my order of the Nursing Tea. Really hope that this can boost my milk supply. I worry that when I return to work, Baby won't have enough. Worry, worry, worry.