It will be too late

Why does my heart ache?
Why do I wait all day,
Only to back out?
Why can't I free my feelings,
From their cage?

Every day, I see you,
And can almost get the words out.
Almost, just almost.
I can never get the words out completely.
And every time I think of it, my heart aches

But I know I have to tell you,
Or else you'll have moved on.
You won't want me anymore.
You'll want someone else.
I have to tell you.

It will be too late.
I have to tell you.
I have to let my feelings fly.
I have to get the words out.
It will be too late.

Why can't I free my feelings,
From their cage?
I can almost get the words out,
Almost, just almost.
You won't want me anymore.

It will be too late.

Hello, Forestqueen! Tassen Spellbinder here to review your work! Let's jump right in!

"Why do I wait all day,
Only to back out?"
-- I don't think you need the comma after day.

"Why can't I free my feelings,
From their cage?"
-- Again, I perceive an unnecessary comma.

"Almost, just almost.
I can never get the words out completely."
-- I think you could replace the period after almost with a -.

"And every time I think of it, my heart aches"
-First, this needs a period. Also, I would remove the and.

"It will be too late.
I have to tell you.
I have to let my feelings fly.
I have to get the words out.
It will be too late."
-- A suggestion: Make the fourth line the same as the first- that way, you would have some really interesting symmetry here expressing the doubts and changing mind of the author.

"Why can't I free my feelings,
From their cage?"
-- Again, unnecessary comma.

All in all, I like this poem. Keep writing!