Lost, it takes some work to retrain your way of thinking, but it can be done. At first, you have you work hard at it; catch yourself thinking negatively and force your mind to think of something positive. This is one place that forcing a smile can really work wonders! I'm speaking from experience here. I suffer from hereditary major depression. I have to fight it on a daily basis.
The more practice you get with redirecting, the easier and faster it gets.
Did anyone in your family talk negatively about people who liked themselves when you were young? I wonder if you're somewhat afraid of making yourself special to you, equating it with conceit?
There is a huge difference between a healthy self-love and an unhealthy self-obsession. Think of your children - If you work on this for no other reason, remember that kids more often than not model what they see at home. Love yourself so the kids learn to do the same.
You are special. You are worthy. You are a wonderful person.