I've written this poem and would like for someone to tell me the mistakes I have in it, and how it's written. Thanks!

In my dreams, creeps up a guy,
Mysterious he is, as I know him not.
He smiles and I gaze-with a heartfelt/heavy? sigh,
Daydreaming often of a true love knot.
His face personifies beauty,
From his perfect chin to his silken hair,
I would love to die for him as duty;
For nothing more would I ever care!
When he pulls me close, I almost faint
For he is strikingly amazing
He has a face of an angel and deeds of a saint
It’s very hard to stop gazing
Then all of a sudden he falls dead
My eyes pop in shock
But I wake up and find myself in bed…
Stupid alarm clock!

-MC

The first two lines bother me, but I'm not sure why. Maybe it's that in both lines the subject and verb are out of normal word order. To do that in one line is not unexpected in poetry, but twice in two lines is a bit much.

The only other things that seem odd are 1) to read about dying and duty in a poem like this and 2) to refer to his deeds when he is just a face to you.

I don't see grammatical errors -- punctuation is needed in places, but in poetry, that's not always a major thing.

The last three lines are excellent!

Thanks for that...so how can I fix this up a bit?

-MC

Re-work line 2. Leave line 1 alone!

Other than that, I'd leave it as is. If you decide you need different words to express an idea, be sure to search for synonyms in a thesaurus:
http://www.thesaurus.com

Your poem has a nice flow and captures a dream-like quality. However, here are some suggestions to improve its structure and grammar:

In my dreams, a guy creeps up,
Mysterious and unknown to me.
With his smile, my heart heavy (or yearning) I sigh,
Daydreaming often of a love that's free.

His face, a portrait of beauty,
From perfect chin to silken hair,
I'd gladly give my life as duty;
For him, I'd have no other care.

When he pulls me close, I almost faint,
His presence strikingly amazing.
With an angelic face and saintly deeds,
It's hard to cease my gazing.

But suddenly he falls, lifeless, dead,
My eyes widen in shock.
Yet I wake up, in bed, instead...
Stupid alarm clock!

-MC

Additionally, consider using more specific and vivid language to paint a clearer picture for the reader.