mama, you seem to be questioning yourself a lot. I just wanted to pop in and tell you that your breastmilk is perfect for your baby. We all want to make sure that our babies are getting everything that they need and that they are healthy. Our mama instinct is sometimes clouded by worry Your baby is doing all of the things that babies are supposed to do. Grunting is normal because their digestive systems are developing. Sometimes it sounds like it hurts them and as their mothers we just want to take the hurt away, but the grunting doesn't mean they are in pain And spitting up is normal, and can be caused by a number of things. Sometimes it's a developing sphincter muscle at the bottom of their esophagus, sometimes it's an overfull tummy, sometimes it's because they have an air bubble trapped in there somewhere - but the important thing to remember is that it is all normal. When spitting is not normal there will be other signs, such as a painful cry as they spit up, pulling their legs up to their chest, etc. Also, some babies have a strong need to suck, and it doesn't mean that they are hungry. When you are breastfeeding, your baby can suck on your breast in a way that doesn't encourage a lot of milk flow, so they get their sucking needs met. They can't do this with a bottle as there is always milk flowing out of it. Maybe you can bring your baby to your breast to help meet those sucking needs, or try letting your baby suck on your finger. A need to suck doesn't necessarily mean that baby is hungry.
You are doing a great job mama. Don't forget that.