Can not think straight and depressed after drinking alcohol

I have been suffering from depression for over two years but a week ago i went for a walk and i had a really long hard think and a somthing just came in my head which i thought i woud never think and that thought was why should i feel down and depressed so i decided that i would stop thinking like this and i would try to feel positive and try to get on with life without feeling depressed as life is to short too feel unhappy but as anyone knows who suffers from depression it is easy er said than done that is why this feeling was like a lighting bolt hitting my brain and i dont know how i done it. But the problem is a freind of mine asked if i would like too go out for a drink as i dont really drink alcohol as much because it makes me more depressed i decided that i would because i was in so much of a good mood and my mind felt clear i said yes but after drinking so much the depression and negitive thoughts are creeping back in head. Could it just be the alcohol still in my system which is making me feel like this?