You're wondering how to send him to his knees for the third time, and he's not even in love with you anymore. That is the message you need to understand if you are a mature woman who wants to know how to get your boyfriend to his knees. If your boyfriend is only having sex with you because you are getting old, then there is no hope for you. But if you understand the dynamics of the threesome, then you can use it to make your old boy jealous, and eventually, get him to propose to you on a threesome basis!.