I need to improve my English

I become I began to study English three years ago. I decided to  it because it there is an important language today; but it's more difficult to for me. I think that I'm not able to improve at English.
On the one hand I haven't a lot of time to study. When I arrive at home after working, I'm very tired and I have to do the housework.
On the other hand I haven't any self confidence. self-confident. English has been my difficult all my life. I really want to improve at English but I'm very discouraged.
In short, when I have an exam, I never know how study, to learn.