Why do I feel like this? What am I supposed to do?

I wish I could offer something better than this, but honestly the real answer is just live your life as best you can and wait. You are still growing and developing even as we speak. I am sure young people are sick of hearing that this is what youth is. I think what happens is that when you hit adolescence, your cognitive development makes big strides and you are now able to think in a whole new way that you didn't when you were still a kid. Suddenly you are confronted with things to think about and react to and try to figure out, things that you never had to deal with as a child. It's pretty overwhelming. Everything you say sounds familiar to me and I am tempted to say it is normal, as long as you don't flip out. So it's something to be gotten through without going off the rails. You didn't make the emotions up, but they can be changeable, thankfully since that means many of the negative emotions will pass as you continue to develop into your 20s. If you feel guilty, that must be a leftover from childhood, because classically children blame themselves for whatever goes wrong, especially in the family. Because children are self-centered, they have magical thinking and believe that everything is because of them. Gradually you get over that (hopefully). I would really urge you not to give in to staying home just because you think you don't look good. Look as good as you can and then really really try to put your attention on what's going on instead of how you may appear to others. Tell yourself that other people are not judging you as much as they are worrying about their own looks--and it's true. You have to make an effort, otherwise you will miss some really fun and interesting events for a not very good reason. Make sure you have at least one or two good friends you can rely on for mutual support. Don't shut people out. We're all in this together. And we are all creating the problems together, as well as the solutions. The other advice is to do whatever you can to get regular exercise into your life. It's going to make a big difference in how you feel. There are days when you may feel as if you weigh a ton and your limbs are soo heavy. Maybe moving around calls your attention to your body when you don't want to think about it. You just have to push through and do what is necessary to make your body more active. It will pay off in many ways.

Don't be so hard on yourself. Try to find humor in your life each day and share it with others. Connecting with people will help; isolating will harm. Your mother understands that you snap sometimes, but it won't hurt to say sorry. You will both feel better.