Well, there's no magic trick, really. All we could advise you to do is make more and more efforts, because only you
can solve this problem of yours. Don't
give up because there seems to be no results. With time, I'm sure it'll come!
Not having friends is a terrible feeling to have, since friends are essential for you to evolve, not only as a social human being (that we all are), but also as a person, as a mind that thinks and observes, as an identity you're constantly building up.
It is weird that you actually have no friends at all. Maybe you should work on your confidence first, since you always sit away from everyone at school. Clearly, that doesn't help. You need to work on your person first. Make yourself approachable. To do so, you need to set a couple of goals, and reach out for them. When I say goals, I'm talking about goals directly involving you: your appearance, your way of interacting, your way of thinking. Reinvent yourself. If you think your body needs more attention, go out and work out, eat healthy, sit under the sun for a while. When talking to family, think wisely before opening your mouth. Try to get closer to your family members: surprise them, support them, don't hide away from them.
If you notice you're too shy when other people are around you, try practising at home, in front of a mirror. Look at you, smile at your face, talk to yourself, motivate yourself to not be afraid of others. Tell yourself you can actually get over this situation. Think about the people that are still yet to come in your life!
Go out for walks, see the world, take a sketchbook and sit in a park; draw, write, paint, watch the birds, the lake, the clouds. Look at how other people interact. Run around, be crazy!
Having friends through the internet may help also, but make sure you reach out for your in-real-life mission that is getting to know more people. Eventually you'll make it!
I wish you good luck, my friend.