You mean, you’ve never taken the necessary steps to build true muscle. Most often this is due to either a lack of progressive overload or inadequate nutrition, or both.
Everything.
You should start a training log and pick a program, and log what your workouts are and what you eat, and read other people’s logs, and ask questions! You have gotten bigger. But the way you’ve worded these posts leads me to believe you probably don’t have a solid diet and workout plan in place. If you do 5/3/1, eat at least 1g/lb of protein and at a slight caloric surplus for the next 5 years, I promise you’ll rescind your “never been able to build true muscle” comment. I say years because that’s how long this takes. Fat loss can be significant in one month, but one month isn’t shit in terms of muscle growth.