How to stop feeling sad over nobody liking my Facebook pictures?

[LittleMonster]

I'm an 18 year old girl, and I have about 500 friends on Facebook. I try not to get down over these things because I know how ridiculous it is to let Facebook upset you or ruin your self-esteem. I've been told I'm pretty, and I try to upload a picture now and then onto Facebook and I try to make sure it's a nice one. I changed my profile picture just the other day to one that I thought was fairly nice. I never get any likes. At all. Maybe one or two at the most. It just makes me feel like a loser. My friends usually get about 20 or 30 likes on all their pictures. It just gets me down because then I start second-guessing myself or the picture I've uploaded. Like, maybe I'm super ugly. This is so stupid I know, but how can I stop letting it affect me?