cheating with his secretary?

My husband went to a convention in texas with his secretary for three days one of those days happened to be Valentines day. My husband and I had been married 18 years and he had only bought me roses 3 times this being one of them he had sent me flowers to work while away that day. When he returned home and talking about his convention he told me his secretary and him were eating breakfast then decided they were going to smoke. when approaching the smoking area they notice 3 loud fat women there so they decided to go to his room and smoke. I got very angery and proceeded to tell him that smoking in his room was not appropriate. this then started an argument because I was accusing him of sleeping with his secretary and I was just an insecure bitch making shit up in my mind?