I'm Always Feeling Low And Wishing Something Bad Would Happen

I'm always feeling low and wishing something bad would happen to me recently split up with my girlfriend and constantly thinking about her I'm paranoid as hell round people and have anxiety in a bad way I have been on anti depressants before when I went through a similar stage just feel like it happening again and can't talk to know one cause I just feel like it's in my head and I not know what to do is it me who is crazy just feel like no one ever believes me what is happening and can't seem to shake it off and often wonder is it me