I've taken him to the vet for blood work and tests. They said there is nothing wrong with him. He used to be really fat, around 18lbs. He's now around 11. This has been over years he lost that but the vet said the blood came back fine. He's not aggressive he just swats at her and chases her but not hissing and growling. I was thinking it was maybe she was acting a different way that has him doing that.