I want to recreate my world with all of my buildings but I'm unsure if the seed has my buildings built-in? will the seed of the world save my buildings?
The seed of the world does not change if you change the world. If you recreate the world using the original seed and the same world generation parameters, the world will be pristine and exactly the same as when you started, with no changes you've made to the world persisting. If you wish to preserve your changes, you'll need to use a tool like WorldEdit or Structure Blocks to transfer your buildings over to the pristine world.