I can't produce enough breast milk. Should I consider infant formula?

Actually you need to know how much is enough. For me, enough is when baby is satisfied and producing enough wet nappies. Don't compare yourself to mummies who produce more than enough to have a stash in the freezer. Having low supply is a rare problem when breastfeeding because most mummies are naturally able to produce to meet baby's demand. If you decide to supplement with infant formula then you may fall into the top up trap, and you will end up having even lesser breastmilk because baby is satisfied with formula and doesn't demand at your breast. To increase your breastmilk, try taking boosters like fenugreek, lecithin (for quicker and faster letdown), oats, milo, almond milk, salmon and other fishes. Do hot compress before feeding/pumping and massage your breasts regularly. Power pumping also helps a lot in boosting up milk supply and the effect is more lasting in my opinion.