If you are breastfeeding well,introducing a bottle of formula can make things difficult for yourself. The baby can refuse the breast for the easier bottle,you can lose your milk supply - based on supply and demand, the less milk your baby demands from your boobs,the less your boobs make - and it can really upset their tummy having formula. Or none of those things can happen, & it might work really well for you! I had a lot of trouble getting BF established due to a range of issues. This meant I was expressing for most feeds & giving EBM in a syringe at the start, & I gradually reduced EBM as the baby was able to feed from the breast. Now I do give one bottle of EBM (expressed milk) in the evenings. It works well for us, but we had issues to start with - if you are feeding well, I dont know that I would mess with that! Personally I would try to express &give that milk before formula, just because it is less likely to mess with your supply that way. If the baby is waking hourly, I would give the EBM at the first wake up so they have a full tummy, & see if it improves at all. If they still wake hourly, then they werent waking because of hunger. Ultimately,do what works for you! Good luck