Your drain is probably clogged if the water in the sink is backing up whenever youre using it.
Oftentimes, this is due to the build-up of oil in the pipes.
If its not the oil, it can be pieces of food that prevent the water from flowing.

Image by: Natural Cures
Read on for the full instructions.
Once the water starts bubbling, turn off the stove and pour the water down the drain slowly.
The hot water will melt the built-up fat in the pipes of your kitchen sink.

The texture from the salt will help remove any remaining fat on the pipes.
Pour the soapy down the kitchen sink drain.
Wait until it all goes down.

The detergent will help dissolve the fat in the pipes melted by the water.
Pour boiled water down the kitchen sink to remove any stray pieces of food.