Hi Andy! Welcome to iMore. Once we know which iPhone you have any might be able to give you some suggestions that will help you adjust to not having a back button.
Welcome to iMore. Apple's iOS does take some getting use to compared to Android's back button. It happened to me as well when I switched over years ago and haven't looked back, well I have peaked at customization...LOL
Yeah, it’s different coming to an iPhone from Android, but you’ll adjust to it fairly quickly, in my opinion, and once you do, you’ll realize the beauty of using iOS.