I was put in a psych ward , What is wrong with me?

I am a 17 year old female, I am in grade 11. When I was 15 I was put in a psych ward because I was trying to kill myself and other people as well as self-harm. I was paranoid and had deep depression. I have felt on and off paranoid on and off since then. I also am realizing that I am having to do a lot of 'double-takes', where I think I see something but I am not sure, I look back and it's gone. I also am smelling things that the source is not there (smelling a family friend's leather jacket when he is working and there is no one wearing leather.) I am not sure, I always think that someone is snooping through my stuff or that someone is following me. I am confused and can't seem to get answers from anywhere near me. Please help...