Some great advice here!
Sorry you're feeling so low, it seems as if you really are focusing on what you believe you're lacking and not what you believe you have to offer. Write down a list of all your good points and the things about you that friends like and what makes you interesting company. If you honestly don't think there is enough in your list, then find something in life to get passionate about, maybe art or clubs you can join or bands you can follow.
Not only will you grow then as a person but you may then meet someone who shares those interests along the way. If you don't yet believe in yourself you may find it's not the right time to get into a relationship as you'll be relying on them too much and feeling not good enough. I suspect, right now, you do have interesting views to hold a good old conversation and that's what holds a relationship together.
Looks can attract attention but so can bright clothes and a bright smile and a confident walk. One of my friends is always asking men out, they don't all say yes but they are always flattered and impressed by her and she feels good just having had the conversation with them. We're all just humans, full of self doubt at times and it's really for you to decide what you'd like and then go and get it! Why should you deserve any less?