The sonnet that I believe that you are referring to, is a deeply moving piece called Sonnet 71. It happens to be my favourite sonnet, so I will recall it here for you from memory.
No longer mourn for me when I am dead
Then you shall hear the surly sullen bell
Give warning to the world that I am fled
From this vile world, with vilest worms to dwell:
Nay, if you read this line, remember not
The hand that writ it; for I love you so
That I in your sweet thoughts would be forgot
If thinking on me then should make you woe.
O, if, I say, you look upon this verse
When I perhaps compounded am with clay,
Do not so much as my poor name rehearse.
But let your love even with my life decay,
Lest the wise world should look into your moan
And mock you with me after I am gone.
Try reading it only on the punctuation, you will run out of breath!
No longer mourn for me when I am dead
Then you shall hear the surly sullen bell
Give warning to the world that I am fled
From this vile world, with vilest worms to dwell:
Nay, if you read this line, remember not
The hand that writ it; for I love you so
That I in your sweet thoughts would be forgot
If thinking on me then should make you woe.
O, if, I say, you look upon this verse
When I perhaps compounded am with clay,
Do not so much as my poor name rehearse.
But let your love even with my life decay,
Lest the wise world should look into your moan
And mock you with me after I am gone.
Try reading it only on the punctuation, you will run out of breath!