i got my betta from aquarium co-op it was in a tank full of schooling fish atleast 20+ should i still be worried?
I don't want to scare you, but when members ask questions or issues, we try to be honest and helpful.
Fish in store tanks are not usually in ideal conditions. The store expects (hopes anyway) that they will sell them quickly, as feeding and maintaining fish costs money. The conditions are generally not ideal due to lack of necessary aquascaping, too many fish, wrong mix of fish, deteriorating water conditions, inappropriate water parameters, or flow-through water from tank to tank to tank which is about as bad as it can ever get for a fish.
Fish housed under these conditions are not going to be at their best, and they will exhibit different behaviours and traits because they are under stress. Think of it as you being in a closed room full of people with no escape and constantly shouted at; that gets frustrating, frightening, stressful. The fish has no escape, so it usually withdraws.
Once it is home in a proper environment, it will hopefully begin to settle down and behave "normally" for its species. Fish traits, needs, behaviours, etc. are programmed into the species by evolution. We cannot change these, so to have healthy and "happy" fish we research the needs of a species and then provide the closest we can to what the fish "expects" in life. Anything contrary to this is cruel to the fish, and not likely to be successful. Sometimes an individual fish may behave contrary to the norm, for reasons we do not understand--but this is common with all species,including humans, so it should not surprise us. But expect the norm and provide for it, and you will be guaranteed of success.
Male betta are not community fish, and they should be housed alone. This will ensure they are free of most stress, and they will be healthier and live a normal lifespan. And another aspect of this is lifespan--fish that do not reach the norm for their species means something was wrong, genetically sometimes but more often with their environment. Stress can be unseen by us until it is too late. Have a read of Loiselle's comments in green in my signature block. The blue comment from Nathan Hill is also relevant, but Dr. Loiselle has years of fish husbandry as a professional ichthyologist.