Unable to concentrate and feeling disinterested in studies

I am studying eleventh standard.
I am from chennai, tamil nadu, india.
I, sometimes, really feel disinterested in studies.
I hate living. Many times, i ve thought about achieving something. But i am unable to follow what i do say. I wanted to score more marks. But i never work for that. Working for that, makes me go frustated. I need to speed up and start studying now for a good future.
I need some advice to avoid disturbances, deviations and to promote interests and concentration in studies. I am helpless now. Hope, u will help me giving, good advice.