How can I gain self confidence?

Okay so every time someone compliments me I think that they are mocking me. But I know that they aren't. Like my friend told me today that I have such a great bathing suit body and I told her to stop mocking me and she said she wasn't and I knew she wasn't. I don't think I'm pretty at all. I have freckles all over my face and I can't put makeup on for my life. I have had the same profile picture on Facebook for 3 months and its me standing by the ocean in the dark and you can't even see my face. I have never had a picture of my face close up on Facebook because I feel like this. I hate it when pretty girls say their ugly because their not and they don't know how it actually feels to be. When I talk to people on Facebook and then I meet them in person they whisper to someone else that I'm much prettier then the pictures they have seen of me. ugh I hate this I want to be pretty or at least feel like it. Can someone help me??�