Are you a pantser? If you're a writer who doesn't plan ahead and you prefer to write "by the seat of your pants," there's nothing wrong with that... unless your results are not what you want. If you're not happy with your results and you're open to trying something new, there are many guides out there that can walk you through the process of outlining your next novel before you start trying to write it.
One guide that I read and found very useful, even if I don't apply it precisely, is Take Off Your Pants! by Libbie Hawker. This book provides you with structure as well as the logic behind the structure. I'm not going to try to summarize it, because there is a fair amount of detail in the book. There is also no substitute for the thinking that you will need to do in order to apply the author's suggestions to your own works. I'm just going to recommend that you get it and read it. I'm definitely not the only writer who has found it valuable. Hopefully you will too.