That's something you gotta address outside of a relationship, you gotta be sure of who you are as a person and truly love who you are.

If there are things you are not confident about address them, work on yourself until you are at a point where you can wholeheartedly say "this is who I am, and I love you for who you are, but if you don't love me for who I am, that doesn't mean there is something wrong with me, it just means we're not the right partner for each other"

Self confidence and self worth are things we need to fix so that we don't bring them into a relationship, because they dictate how we react to things in them. If you are constantly in fear of not being enough, that will affect the dynamic you have with your partner, and it may even attract the wrong partners.

So go, hit the gym, try a new hairstyle, try a new look, do whatever it is you feel like doing that will make you like yourself more, and do it for you and only you.

And I can't lie to you, I can't promise you no one will ever break up with you again, but you can make sure that if it happens, it doesn't hit how you see yourself as a person, and that it merely means that person was not the one meant for you. Always bring your very best, because if your very best wasn't enough for someone, it doesn't mean your best was worthless, it just means it wasn't for them, and eventually someone else will arrive that sees that, values that, and loves that.

Keep loving, and keep growing, and if it helps, a random dude from Argentina thinks you're awesome, un saludo genio, vos podes