Is it okay to give your baby formula as well along with breastfeeding?

Yes it is definitely ok. I did that in my early days as well. If you would like to supplement with breastfeeding: Always give baby breastmilk first (by latching) and then if baby still seems unsatisfied you can give him a bottle of formula to top up. If you would like to supplement into expressed breastmilk: Always prepare the milk separately and not using breastmilk to replace the water. That means to say if you would like to give baby 4oz in total then u would prepare 2oz of formula first (according to the instructions on the tin) then adding another 2oz of breastmilk to the bottle; or whichever combination you desire. However if baby is too young feeding from the bottle may result in nipple confusion and baby may end up refusing to eat from your breasts. If you're worried about that you could do spoon feeding or feeding from a cup. Also if you are struggling with supply, then bottle feeding may lead you to the top up trap. You may produce less because baby demands lesser at the breast and you end up with even lesser supply.