Can someone help me to learn I shouldn't be scared by this?

So I love my boyfriend. Way more than humanly possible I'm sure. Well he told me that the girl he asked out before me said she has a crush on him and he told her she missed out. And I believe every word of his to be truth. But now that there was slight compition I'm overwhelmed. Alot of my ex's abondoned me out of now where or cheated and I love my boyfriend and don't want to loose him again. I've loved him for years and now that he's mine again I want to keep him. And it might be hard to believe because I'm 15, but I know he's the one made for me even though it's long distance right now. Can someone teach me not to be afraid and be confident in myself and not feel so scared? Thank you.