Don't get down on yourself about it. Just do it the right way.
You think you hurt bad now, imagine what it would do to you to have your proposal shot down? A proposal should come when your relationship is stable and both parties are committed to having a great, lifelong relationship together.
Case in point: my fiance. He was dating some girl for almost three years, and it was pretty rocky from what I understand. She couldn't make up her mind about being with him, and he proposed to her (I think to finally get her to make up her mind). She said no, got angry, and told him he was just trying to "hold her back". It still stings, I can tell when he talks about it.
Live as if you were to die tomorrow. Learn as if you were to live forever. - Mohandas Gandhi