Dear Arc Flash readers: My boyfriend only proposes during sex

pls Arc Flash Reader, i really need your help here i have even send same to other blogs too
My boyfriend only proposes when we are making love...in the heat of a passionate moment he says things like 'let's get married', 'marry me', 'when do you want to get married?' But once we are done, he doesn't mention it again ...and I'm too shy to bring it up. What should I do?