To be able to help you we will need a bit more information.
How long have you had the betta?
How long have you had the tank?
Did you cycle it first?
Do you have a filter?
Do you have a heater?
Do you have an internal thermometer?
What temperature is the water in the tank?
What size is the tank?
How often are you changing water?
When did this behavior start?
What are you feeding and how often?
How much water each time?
What chemicals are you adding to the water?
Can you get a picture of your betta? Pictures can be very important in determining possible issues with fish.