Does anyone else ever feel like this?

Yes I sometimes have the same symptoms as you. Because I have clinical depression. You need to get some help before you end up actually hurting yourself. I have many times and I'm lucky to be alive. You are not to young either, mine started when I was 13. Usually the only help is medication. You are not being selfish, depression is not a mood or an attitude, it is a chemical imbalance in your brain.