You have to dedicate energy, time, and commitment by putting the relationship ahead of other relationships and really working to spend quality time together. It usually is an insecurity about your body or technique. Maybe you should take showers together or be in a Jacuzzi together. If you have a problem with your body, then you will have to get over that and realize your partner likes you for you. Don't be afraid to make mistakes in sex.
Body painting is fun also.
You can dip it in chocolate. Find out what encourages her to do that and tell her that you enjoy it. Maybe you can talk about her concerns. Maybe she doesn't want you to ejaculate in her mouth. Maybe ask what she would like.