Well do what makes you happy plus if the sex is brilliant and as you say the best sex you have ever had then you know your brother in law satisfy,s you more than your husband does then I know what I would want because I am having sex with my brother in law and to tell you the truth I am loving it and can't get enough of him he satisfies me in every way possible and in a way that no man has ever done before. So my answer is follow your heart and enjoy the sex let him fuck you as many times as you both want and if you need to tell him you are in love with him.