Not Sure what to do...

OK so i have this awesome girlfriend and I'm so madly in love with her, but I have a problem, there are times when we are talking (texting and on the phone) and I feel like she is not as in love with me as I am her. I occasionally ask her if she still likes me and the response is always nice something like, "I'll always like you. or Yes of course" and things like that. I'm planning on telling her that I love her soon. What I want to know is how do i get her to say she likes me without me asking her?