When you feel lust, you want to have physical closeness. The imago is connected to love. When you have lust and you have sex with someone over a period of time with caring, responsibility and commitment, you then have love. Love and marriage go together and sex and love go together, but you don't have to love someone to have sex. When you have sex with a caring towards another person, it can channel itself into love.
Love is physical and emotional intimacy.
I'm serious about this. That means you possibly did not fall in love when you married. You did not marry your imago. People who don't fall in love and marry for other reasons usually feel cheated and seek this out later. You need to think about whether or not your marriage is worth jeopardizing for this person.