Sick Al-Fi?

A little worried about my boy Al-Fi. I've been treating him for a thing of fin rot, which ended well as regrowth is showing. But his belly has turned white and slightly bloated. He's acting normal if not stir crazy since I have him in a smaller container than his 2.5 gal tank. I might just be a little crazy though, I'm not sure since I've never raised a fish of any type before. Thanks for any input! Even if it's just an internet pat on the head and reassurance. <3

http://imgur.com/a/3jCKA

Housing:
How many gallons is your tank? 2.5 Gallon
Does it have a filter? Yes
Does it have a heater? Yes
What temperature is your tank? About 78
Does your tank have an air stone or other type of aeration? No
Does your Betta have tank mates? What kind? None

Food:
What food brand do you use? Top Fin Color-Enhancing Betta Bits and Tetra Blood Worms
Do you feed flakes or pellets? pellets
Freeze-dried? Tetra Blood Worms
How often do you feed your Betta? How much? Daily, twice a day, 2 pellets. Blood worms on Sunday

Maintenance:
Before your Betta became ill how often did you perform a water change? Once every two weeks then started doing weekly.
What percentage of water did you change? 50
Do you vacuum the substrate or just dip out water? Vacuumed what I can.
What additives do you use? Top Fin Betta Water Conditioner

Water Parameters:
What are your water parameters? Please give exact numbers. If tested by pet store please get exact numbers. "Fine" or "Safe" won't help us help you.
Ammonia: N/A
Nitrite: 0
Nitrate: 20
pH: 7.5
Hardness (GH): 180
Alkalinity (KH): 80

Symptoms and Treatment:
When did you first notice the symptoms? November 6, 2015
How has your Betta’s appearance changed? White bloated belly.
How has your Betta’s behavior changed? None
Is your Betta still eating? Yes
Have you started treating your Betta? If so, how? Not for what is currently worrying me.
Does your Betta have any history of being ill? Just ended treating for fin rot
How long have you owned your Betta? Was he or she a rescue? 7 months. Not a rescue.

http://imgur.com/a/3jCKA (same album as above)


**** The water hardness has been that level since I got him, had no idea how to soften it.
****Recently treated for slight fin rot. Ended treatment today(November 6th, 2015) Fin regrowth showing.

*****Switched from a gravel bottom to sand, did a 100% water change. Added Stress Coat and Water Conditioner. Water parameters listed are the fresh water I changed out. Water and bottom changed November 6th, 2015. He's not in the 2.5 gal yet since the water is still murky from the sand.