I keep everything to myself. It's hard to even make friends for me. I can't believe I'm already in college, and yet, I'm still in this kind of situation. It's really hard for me to catch up already, and I've skipped several classes. I just feel really terrible. I don't know what to do. I'm horrible. I can't really do anything.

I know the feeling, but you have to stay strong :)
Everyone goes through tough times in their own way, and I know you're probably thinking it will be like this forever, but trust me, it WILL get better.
If its hard to make friends, just try to keep the conversation going when they talk to you; smile to people and just be nice :)
Try not to skip, focus on doing it for yourself; it will help you keep up and always ask if you're not sure, the teachers are there to help! \(^.^)/ You can email them if you're too afraid to talk. You're not horrible; and definently not stupid or useless so do not EVER think that you're not worth it
And remember; the world isn't as bad as it seems