Is this a normal feeding pattern for my newborn or is she not getting enough with each feeding?

she is 12 days old and I think she is having some nipple confusion because we had to supplement early, however she is back strictly on the breast and for the most part doing ok with feeding. I know it is normal for them to eat every hour however she eats more often. I feed her for an average duration of 20 minutes straight of her eating. It seems like she is getting plenty, my breasts drain fairly quickly and the flow is pretty fast. Before the nipple confusion she would eat and pass out. Now she eats and stays awake and is hungry about 20 to 30 minutes later. I feel like in one feeding she is not getting enough if she wants more that soon. I basically am feeding her every 30 minutes and she is staying awake. Every newborn I have encountered falls into a heavy sleep after a good feeding. Is this a normal pattern? Should I consider some alternatives like nipple Shields?