Is my wife unfaithful to me

my wife is unhappy with me. we dont get along. she is close to my brother. she is friendly with him. she made allegations before about him. suddenly now she is making allegations as if he made moves. I asked her why she didnt tell me before. she said i dont listen to her.. But i feel she is hiding some thing or proving she is sincere to me. my brother dont visit my home. but i came to know he was at my home when i wasnt around. I was also told by my friend he saw them in car but she never told me. she acts if she hates him. but when she hates why would she allow him to visit her when im not around. is she playing behind my back. she took gifts from him she never told me. now she complains about he is gifting her. what could be the truth. is she ******* my brother too.