Some women do not produce enough milk to satify baby, so doctors will tell you to use formula in place of breast milk especially if you are pumping and cannot be around all the time

I would ask your Health Visitor or at your baby clinic.

heya,
yes you can, make sure it's a formula for breast fed babies. I have used aptimil.
However your breasts will stop producing milk for the feed you suppliment
for if done too much and can be difficult to return.
Its best to try and leave baby on for as long as possible ( even if they dont seem to get enough milk this will tell your breasts to produce more.)Then after a feed if baby is still hungry suppliment. Within 48 hours you should be prducing more.
Good luck!