First off, I know how you feel. I have been there and sometimes I still find myself there. You have a smile that brightens a room, but nobody would expect you of all people to feel so unloved. You disguise the self-doubt with jokes and laughter, but deep down in the pit of your stomach you feel defeated.
I don't know who made you feel this way, maybe it was an ex, or a friend, maybe even a family member, but it's simply not true. You are so loved and so lovable, and any person who makes you feel otherwise shouldn't have the privilege of being a part of your life.
Something I have learned throughout my life is that you can't make everyone like you, and you definitely can't make everyone love you. And that's okay. If someone dislikes you then so be it. If you love someone and they don't love you back then whatever. But don't ever, ever, EVER allow anyone to make you feel like you're hard to love.
The right people will love you for you. Unconditional and unwavering love comes from within. It's what we all deserve. Nobody is perfect, but every single person on this earth deserves to feel loved. Don't try to find your worth in a relationship or friends, first you need to find it in yourself. Love yourself and the right people will come along.
Remind yourself of what makes you so great and remind yourself of the awesome people already in your life that love you. I think of God's unconditional love. He loves me no matter what. That's the type of love we should mirror.
In any relationship you're going to make mistakes. You might unintentionally hurt someone you love, and they may hurt you, too. But a person that truly loves you will love you through the good and the bad. Don't beat yourself up because someone wasn't able to love you. That has nothing to do with you and everything to do with them.
Love yourself enough to know when you deserve better. If someone makes you feel unlovable or you feel like you constantly have to prove yourself worthy to be loved, then that person isn’t right for you. You need to hold your head high and know you can do better. Know that if someone isn't capable to love you that it doesn't mean you're not someone to be loved. Someday someone out there will love you for all that you are.
My sister once told me, "How can you truly appreciate happiness and love without having experienced sadness and heartbreak? Every feeling we have is based on comparison to something else. Good? By what measurement? Bad? Compared to what? At some point you will have people stand by you and you will appreciate them so much more because you know how it feels to be abandoned."
The feeling sucks. Someday because you have experienced the feelings of heartbreak, loss, and lack of love, you will be able to fully and wonderfully appreciate the right love when you finally find it. You are so loved and someday someone will show you what you've been missing out on. For now, love yourself. The rest will follow.