Lizabelle,
Right now you are very depressed and not thinking clearly. That's what this awful illness does.
Extreme guilt is a symptom of depression. Meaning you feel guilty and responsible for things you had nothing to do with. I don't think that means that you think the world revolves around you or that you can control everything, simply a distortion.
I often felt like I "shoulda coulda woulda" done something that I didn't or that I "broke myself" somehow. Thinking like that is fruitless and painful. I can't pin point the second my problems started or the exact reasons why. While causes need to be found for issues to be resolved, regreting and beating yourself up for the past does no good.
Growing up is hard. I'm not done yet, but I know it sucks even without depression. But you can do it!
I hope that you can get to a T and get the help that you need. This isn't something you want to do alone. It's NOT your fault that you are sick and you need help to get better.
Pleas keep us posted, Liz. And keep talking! Sometimes it can really help.