In this write you put on a mask so no one can sees your pain, you feel life is knocking you down and no one cares to pick you up. Then in the last line you said That seems to be the reason for me in your life, like the whole poem is only an explanation why you are in her/his life, only for him/her to stumble over you, to walk over you.
Although I am sure you do not want to, I cannot help to feel sorry. You must learn to pick yourself up and go on with life.
As for commentary type requested you want writing advice, not a real writer myself so this is only a matter of opinion, I like to figure some stuff out on my own, your poem is strait the point, there is nothing to figure out. It is like a skeleton, a very nice one, but there is no meat. I want some structure. You begin with a rhyme structure but lose it in the second stanza, and continue with the third. On the other side you are very honest and most people can relate and sympathize with you, I think this is your style, keep it simple.
But this is once again only a matter of opinion;please don't misunderstand me, I liked it alot; it doesn't make your poem a bad one.