Low on storage (iPhone 6s)?

My phone has been low storage for like 7 months. And I keep getting those notifications, I deleted so many apps since than and my storage is still so low. I have Apple Music that takes up 1GB but other than that I don't have much WTF

The apps that come with the phone, you know the ones you can't uninstall, will automatically update, taking up space. And since you can't uninstall them, you can only uninstall the update, it will continue to take up more and more space until there's none left. Now, there are ways you can uninstall some o these apps but it may cause the phone to stop working properly. I think they do this so you HAVE to get a new phone, especially since you can't add memory cards to it, like for androids.

If you go to [ Settings > General > Storage & iCloud Usage > Manage Storage ] you can see how much each app takes up, and how much space you have left. From what I see/hear, photos tend to take up the most space, and since it is an app that can't be deleted, you'll have to go and individually delete all your unwanted pictures.
Or you could just get a new phone with greater storage, and transfer your original phone backup to the new phone.

If you have truly removed everything that is not needed, then get the app Dr. Cleaner. It is free, safe (Trend Micro) and amazingly effective. We have used it for about 5 weeks now, on our iPhone 6 16g phones, and are very pleased.