I'm 20 and I never had boyfriend. I was in love before, but they didn't like me. I'm so depressed, especially cause I still think about those boys from past.?

Talk to someone. At 20, it's hard to say what came first the depression or no relationship. It could be that you have relationship trouble because you are depressed and/or have self-esteem issues. These are a just a few of the things an therapist could explore with you to help you process some of this.
Don't live in past. Being attracted to someone is not the same as being in love. When you find a good match, the feelings will be mutual. Feeling sad about the past keeps you stuck there. Live today and tomorrow may be happier for you.