I just looked it up for you:

"An average betta lifespan is 2-4 years. The average age of a betta when you buy him in a pet store is 6 months, although this can vary dramatically."

I guess that would explain it!

I used to have a betta. When he died I was horrified. I had nightmares about it! He just looked sooooo sick and it took so long for it to happen!

I know it's just a fish but still - it's a life! So I know how you feel.