Instagram does show new followers in notifications but they disappear after a while and get mixed up with likes and comments. I had the same problem trying to keep track of my account growth. What helped me was using a tool that shows
recently followed instagram accounts so I could see exactly who was new. It's actually really useful because you can follow back people who seem genuine and ignore the obvious spam accounts. Some tools also show you patterns like who follows and unfollows quickly. Makes it much easier to manage your followers and understand who's actually interested in your content versus who's just playing follow games
