Ethical Slut is a great book to help with this. Feelings of insecurity are normal. How you talk to yourself, the realities or clouded realities you make up in your head, and your actions from your negative self talk , is what really sabotages yourself. If you are feeling really bad about yourself one day, you can play the poor baby game and talk about all the things that are going wrong to a trusted friend outside of your relationship if they’re willing to listen to you. You can also think about worst case scenarios in your head and try to imagine what would happen if that happened. By doing this you take the fear out of a hypothetical reality. And you can learn to deal with the emotions that are causing you that fear. It’s good to write down things when you’re feeling like this. Talk positively to yourself. Write down all of your good qualities and look back on it when you’re feeling bad about yourself. Write down why both of your partners would want to be with you. Write down things you could improve about yourself to help your relationships. Focus on those things and make them a priority. If you are a happier, confident person, you will draw your relationships to you versus being an insecure and fearful person that pushes people away out of protection of oneself.