I just joined this forum. I had a Betta that had bloat too. The best we could do was lower his water level and try to let him pass it. I didn't(and still don't) know much about this type of problem as he was my first fish. If it happens again, the most I can say is to give him fiber(peas) and lower the water level. Some bacterial/fungal medications might help to prevent other problems.
I had the same problem with my betta.. Unfortunately he has passed away now, but I tried bathing him in Epsom Salt, and it worked. They do not like this, but feel much better after. Used to bathe him a couple times a week for about 1/2 hour. You can find Epsom salt at Walmart, and other places.
Hope this helps, and I hope and he gets better..