In my opinion i think it was really good. i liked how you didn't make the poem into stanzas, not all poems have to be in stanzas. I also liked how you rhymed your words. Its was good, keep it up.

"I am slowly dying inside."

I like this opening line, although it is short it makes the reader wonder why and how you are dying inside, and what it is from.
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"I miss your touch, the sound of your voice, and the touch of your lips on mine."

The repeat of "touch" here threw me off a bit, maybe replace the second "touch" to "caress" or "feeling". It would read a lot better.
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"As I wonder when your gonna care, I soon realize that you are never gonna be there."

"going to" sounds better than "gonna" and its proper grammar, so my suggestion would be to change that if you want.
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"Every night I cry myself to sleep wondering why you aren't with me anymore."

This line was a bit cliche, and I think you could be more elaborate and creative. Try using unique words and lines because this is really overused, that's just my opinion though!
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"Couldn't you tell that you mean everything to me? You always said that all you ever wanted was for me to be happy? Was that a lie? You said you loved me. Did you really mean it?"

I love these questions here, they really make the reader think about all you are saying. Just one thing, there should be no question mark after the line: "You always said that all you ever wanted...." It is just a statement.
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"I keep thinking what do they have that I don't and its that they have you."

For better understanding maybe re-word to:

"I keep thinking, what do they have that I don't? Then I realize its that they have you."

Changing it makes it clearer for the reader.
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"They better love you more than I ever could because thats the only way I can cope with letting you go."

Good emotions here, "thats" should be "that's".
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"You're not worth the tears, the heartache, the pain, or the emptiness."

An expressive and heartfelt line, I liked this.
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"I don't know why I gave you the time and why I wish you were mine. As time passes its making it harder for me to move on. I think I'm finally giving up on what I promised myself I'd never let go. Please don't expect me to be strong. Would you be strong if you lost everything that mattered to you?"

Great job here, there was a lot of emotion and deepness, you truly pour out your feelings and thoughts here. I love how you tagged on the question at the end, very clever, because you just told him to not expect you to be strong. Then you ask him the question, nice job.

4/5 from me, I thought there are many points where you can go back and touch up, it felt rushed. Also, why did you suddenly rhyme in the ending? It threw me off, so either do all rhymes or no rhymes. It will really read and flow better.

Take care and God Bless!

~MaryAnne