Are my fishes going to die?please help,before I'm going to sleep?

I have had my fish for 3–4 months, it is that kind of fish that need to stay in tank alone because they eat each other (BETTA). Mine is male. today at pet store sell-man said my fish can live in the same tank only with 2 females. so I bought them. and now I’m worry he can eat them :( please, did some one had this kind of fish and REALLY know can I go to sleep and don’t feel guilty in the morning or should I separate them now??