Bettas will still make their bubblenest while sick, depressed, healthy, whenever. LebronTheBetta made an informative thread... If I find it I can post the link here if you want!
Your water's temperature should be much higher, and be around 77-80F roughly.
EDIT: With the heater make sure you acclimatize him slowly to the new temperature, slowly bringing the temperature up a degree every hour until you have reached the proper temperature!
Out of curiousity, what sort of food do you feed him? Brand name? How many, and how many times a day?
I made this post on your other thread, but it appears you made a new one... SO! xD