Truthfully this could use a bit of work. For starters, try not to use 'U' instead of You in any kind of writing, espeically poetry. Even more so than stories, poems have to really flow in order to grab the attention of the readers and there should never be any apprevations in poetry. Also noticed a few grammar mistakes such as 'wont' instead of 'won't', 'endliss' instead of 'endless' and ain't should never be used in poetry, whether it's considered a word or not, it's not a poetic word and tends to interupt the flow.
I noticed a few problems with your stanzas as well. For starters, there's no breaks between them to show when one stanza ends and the next begins. Also your meters are a bit off, the first stanza shows a pattern of AA, BB, CC, D but then the third stanza, which seems to begin at 'As I watch them slip away' judging by the earlier stanzas, goes AA, B, C, D, EE. And from there the meter just keeps randomly changing. No matter what pattern you chose to put the stanzas in, they should remain the same throughout the poem.
Also there is really nothing to link this poem to anything Sesshoumaru and Kagome related, now I am not sure what the rules of the site are when it comes to poetry as it can be a bit harder to make sure the readers can tell it's about them, but perhaps you can add a short AN to at least confirm that the poem is in Kagome's POV and that she is at least referring to Sesshoumaru at some point in the poem.
And in case you do not understand what I mean by meter, I'll explain it using the first stanza of your poem...
'It all started with my heart
Then a boy came and tried to tear it apart
As I sat there with all my tears
You came along and settled all my fears
Now as we are together U and Me
I feel the pieces coming back to me
But as time goes on'
With the first two lines, heart and apart rhyme, it's AA, simply because you always start with A :).
Then the next two lines, tears and fears rhyme, but since they do not rhyme with the other two, it's BB
Then the next two lines, even though they are the same word, it still counts and since it is once again different, it's CC
Then the last line by itself becomes D.
So the meter for this stanza would be AA, BB, CC, D. Hope that makes sense :).