I know it has been a week since you last posted but I hope he is doing a bit better. I would like to point you to this thread:
http/www.fishforums.net/index.php?/topic/423362-betta-splendens-caresheet/ as it will explain the best way to keep your betta healthy.
From your photos, your betta is extremely bloated. With the small size of the bowl, not enough water changes, and no heat being the reasons your betta is in this position. That is a very small bowl which would need AT LEAST a 100% water change per day to keep the ammonia level down low enough to keep him somewhat healthy. It is also too small to reliably heat which is an issue all to itself. Bettas require a heater to keep the temperature stable at no less than 78F. When the water is cooler than that, their immune system is compromised. Another issue of cool water is they tend to have a harder time with digestion since the cooler water slows their metabolism down and they are less active which means they need less food. I don't personally suggest peas as a laxative. I suggest frozen daphnia as it is more like what the betta would eat and it works great as a laxative. Just because he has lived for 9 months in that tiny cold bowl does not mean he is happy. Clear water does not mean clean water as dangerous levels of ammonia do not change the way the water looks. Which is why regular water changes are so important. I recommend getting a bigger container for your betta so that you can heat it reliably and not have to change the water quite as often.