Why do I feel this way? What will i do?

I have times where I am happy and so joyful .... and I wish they last longer but when those moments finish , I feel so lonely and the " now what ?" Feeling . I feel like I am living in an imaginary world where I just pretend I am happy in my mind and having all those fake conversations that 100% wouldn't happen . I hate this . sometimes I would be very happy but then when it's over . I feel so very hopeless and again back to suicidal . I just don't know what will I do anymore . School is about to finish ( I don't like it ) but at least I was able to talk to some people there . Now finals are coming , I just don't want to study I don't have a hope for passing ... even if I did , I always wonder so what then . What will I do ? I don't want the same killing routine I have every summer ... but I don't know what to do to be happy . I want to die but i am scared of committing suicide and I wouldn't want to hurt my parents .