"I want to matter to him." The tone of this line is so angsty. I love it.

"But now it's like there's a gap between us." This line in itself isn't that creative, but the formatting of the poem is. I like that you created a "gap" to physically show the "gap" that this man has left in the speaker's heart.

I know how that feels...

Easy to read and understand. It's easy to relate to the speaker.

Well done:)