Bloated or partially clogged drains can be caused by a variety of factors, including grease from food waste, hair, and soap, as well as tree roots that grow into the pipe. Additionally, poor drainage systems, combined with heavy rainfall and poor maintenance, can also contribute to blockages.
For more complex blockages or if you're unsure about how to proceed, it's recommended to hire a professional plumber to clear the clog. They have the necessary equipment and expertise to safely and efficiently unclog your drain.