How could I possibly ever be happy with my body or me?

Listen to the conversations you have with yourself and start to realize they are negative and turn them around. Self-esteem is your ability to deliver on your self-promises, but self-image is simply your perception of yourself. Changing both is easy, but takes time - Examples:

Simply choose the new image and focus on it daily. Repetition and results can create faith and belief.

For the self-esteem, start honoring your own promises. You'll be amazed at how confident you become when you don't sell yourself short.