the same experience happens in my life also. once i have propsed and tried to to make sex with her. she had declined. many times i had tried to touch, kissed.many times masterbaution is the only hepful.
its all about our ags, imagination and fantasy.
once you love a girl,look and love outside world, your sex enery will divert.
OR
tell toyur love honestly, frankly, softly to her in right, alone situation
best of luck