Finding someone you trust to talk to about this is a great idea! It's hard when you have people constantly pointing out your insecurities, but try to remember that you should only ever be striving to look like what YOU want to look like. You are the most important person when it comes to your looks. Unless you're speaking with a doctor, any comment about your weight should be disregarded. Any one else is trying to push their own image of beauty onto you, and you don't have to deal with that.
At 14 your looks are going to rapidly change any way, and I know it doesn't feel like it, but what you look like right now really isn't a big deal. If you really can't find anything about your looks you like, just remember that you have a hundred other things about yourself worth celebrating, like your talents and personality. Again, it might not feel like it, but those are way more important anyway.