hello and welcome to you. :)
can you please tell us more about your betta please.
size of his tank,temperature of the water,test kits results,
food you feed him,how often you clean his tank,do you use a
dechlorinator for the new water,do you replace the old water with
new ready warmed fresh water.
anything else in with him,when you bought him,is there a filter,and
if there is who do you clean it.
i know this is a lot of questions for you at this difficult time,but if you
can answer as much as possible,we hopefuly can help.