I think this is okay. Very honest, which is good, but it's also kind of angsty in some parts.
I got confused. You started out by saying that the person is the reason you cry and stuff, but then it turns into you saying good things about them. I guess thats nothing to be confused about though. That's how all relationships are. No one's perfect. But hey, if we were all perfect, what would we learn?
No offense, but you don't have to be so redundant.
You are the reason I'm up every night crying
I feel like I am dying
I can't sleep at night
I want to hold onto my pillow tight
I always think of flowers
The reason that towers
I try to fight
I have no more fright
I live my life
It's just a lot less redundant that way, and I think it still has the same weight. The poem is kind of weird in that the first part of the poem, this person seems to have scarred you emotionally, but it in the second, this person is the one you love. I suppose I've known people in similar situations. I think poetry about "serious" subjects is generally better if it doesn't rhyme.