Just so you know, I have personally found it very difficult to build blocks or squares after using CFOP for so long. Using white cross also made it very difficult for me to adapt to other methods. For Petrus method, when building blocks, I always tend to make pairs and insert them because I'm so used to that. This is why I gave up on learning methods other than CFOP. CFOP is one of those "brain dead", "stupid" methods. It's too easy, that's why it's difficult to adapt to different methods after using CFOP for so long.
Don't worry though, since you have only been using CFOP for about a month, it shouldn't be that bad. But I would recommend learning at least one of the methods that Kirjava listed so you can get used to block building also. Try also building blocks on different colors, not just on white (or whatever color cross you use now).