The Overflowing Bra

Ok start.  Needs more character development.  Grammer is horrible.  I had to stop reading because it reads like a stream of conscience. The ideas jump all over the place. 

Keep trying

This is a hot story. Don't let the grammar police get you down. I am not going to get off on punctuation but I am going to get off on sex and continuous growth. Keep writing and posting.

your grammer and spelling were off, but still a good story.

Glad you posted.  Like your concept/kinks.  But re-work, re-read, proofread your stories before posting.  Don't get discouraged.

A classic premise & likeable characters, but the story is choppy and would benefit from some technical improvement. My suggestion is to keep writing and have another person read your story before posting, an extra set of eyes often finds the things we overlook ourselves.

The problems mentioned, especially the paratactic style and homophone errors are common signs of dyslexia. I have it so I know. They however aren't grammar errors. The first is an rhetorical error and the second more an error of vocabulary. Be kind, if it is dyslexia, he may be doing about as well as he is able, and improvement may be very slow or impossible.
  

I think it's wonderful that you started writing, but maybe you should get back at it after you've passed 5th grade. 

You've got a rather nice idea for a story there, but as the others have stated, your writing isn't good enough (yet) to deliver your idea well.
I will try not to repeat what others have already said and point out some more flaws:
You should train up on your (written) English, since you made quite a lot of avoidable mistakes, especially with mixing up homophones (words that sound alike when spoken) like their/there.
Another thing that makes your story hard to read is the fact that you used a paratactic style of writing (simple sentences without sub-clauses) with almost no conjunctions. You don't have to get overly complex in your structure, but combining and connecting sentences makes for a much smoother read.
On a side note, I don't think that many people will like the "peeing" stuff very much. I don't want to restrict your writing, but if you want to reach a broader audience, you should think about leaving rather "special" stuff like this out of your stories. For me at least it more or less ruined some of the best moments of the story, which resulted in one point less overall enjoyment rating from me.
If you heed the advices of all those who commented here, I encourage you to write and submit some more stories. You do seem to have some interesting ideas in your head ;)

You have a great start here.  However, as others have mentioned your grammar is sorely lacking and the detail in various parts of the story varies wildly.  You need to create a more smooth consistency in your writing and an editor or a draft review process would go a long way into making this story a much more enjoyable read.  I would be happy to edit for you if you wish.  My email is UltimaNemo@yahoo.com. 

I get the feeling that English isn't your primary language. Like many have already said, having someone edit for you will help your writing mechanics.

You should definitely edit your writing. If you're interested in writing, read the old standby Strunk & White's Elements of Style. In addition to that, practice proper construction and pacing. Your pace was too fast and breathless, lacking in details until the expansion scene, where instead of being bereft of details, it was merely lacking in details. Its good that you're writing and practice makes perfect, but definitely pass your stuff through more than one review. 

you definitely need an editor and u need to look over your work, the sentences were so distracting and disorganized that i could not even finish reading it. maybe u should put more time into it on ur next attempt

You need an editor to look over your work before you submit it:  there were a lot of very basic errors that could have been fixed on a glance-through.  (Just for starters, you have to study up on where paragraphs begin and end -- and a spellchecker will never catch homonyms.)  This feels like a single-run writing session that went straight from the keyboard to the upload stage with nothing in between.  It's very hard to read, and that covers multiple levels -- going with that small a font isn't kind to anyone's work.  The characters need more personality, and some of the scant descriptive information we get about them comes late...  
It's a first effort, and there's room to improve.  But you're going to need some advice and help -- and you'll have to follow it.
And for the record, going up one cup size doesn't destroy a shirt.  Not even a really cheap shirt.