Male Betta - Swollen Abdomen

Question
I've just noticed that my male betta's abdomen is swollen, maybe half an inch or less. I cleaned out his tank today and treated it with a betta treatment tablet. He's still swimming around, but not as much as he use to. I really don't want to lose him, I just got him a few months ago. He was fine a few days ago, its been about five days since I cleaned his tank, not counting todays cleaning. If you know of anything I can do I'm all ears.

Answer
Lura,
Sounds like he might be suffering from constipation. Fast him for 2 days. On the third day, feed him a cooked shelled pea, and then fast him again for two days. If this does not work, the do the whole thing again. A Betta's stomach is the size of his eye so it is very easy to over feed him. Let me know if this does not work.