How big is the enclosure?
When was the last time you changed your water?
How do you change it?
What additives/chemicals/anything do you put in the water when you change it?
Is it heated?
Are there any tankmates?
Does the fish look any different lately?
Filling out the answers to the questions in this form: http://www.bettafish.com/showthread.php?t=49233will give us the information we need to make a diagnosis and give you appropriate advice. It is easiest to simply copy and past the form into your reply and fill the answers in. The more detailed your answers, the better the quality of the advice you will receive.