Wasted love: a sonnet

Here's my first attempt. See if you can find the one iambic error:

I'm ten years old when first I fall in love
And Jennifer is my beloved's name.
An angel who has tumbled from above,
She kindles in my heart a burning flame.
And when she asks to be my Valentine,
I can't believe what I am being told.
She offers me her heart; I give her mine,
Together with a chain of fakest gold.
But later, when she gives my love the sack,
Repudiating every vain embrace,
I make it clear I want the trinket back
And, tearful, Jenny throws it in my face.
Misunderstood and unrequited too,
My love found none deserving until you.