help with grammar/structure of poems?

Ok, so this is a bit of a personal poem and probably wont make sense, but I was just hoping people could give me some advice on the structure, how to include the parts that didn't rhyme with the bits that did without ruining the flow of the whole thing and just generally ways to improve
I'm also not sure about the grammar, I've forgotten everything I've been taught about poems and where to put commas and capitals etc Thanks.

It was just some girl
Just some breast
A moment of weakness.
I did my best
To move on.
To forget.
To pretend It hadn't happened;
Yet, there's something eating away at the core of my brain,
Ive never been one to pass all the blame,
All the responsibility for whats going on
Onto someone else, you know you did wrong
But what I don’t get, is you won't admit it,
Won't give me the closure I need to forget it
And right now, I don’t understand
How I feel this betrayed.
In technical terms you've done nothing wrong,
Just fueled the fire that burns beneath my insecurities
apart from a minor indiscretion, Its my problem to resolve
my evil thoughts
my abnormal demons
and I don't want to push you away
but if I continue like this, I know you wont stay.
And I'm just so confused, I don't know what to do
because I know my problem doesn't lie with you.
It was just some girl,
Just some breast,
A moment of weakness
I did my best.

Try not to be too worried about things like grammar and structure. When I write a poem it actually contains no structure and is wrote in the format of any story and they barely ever rhyme. Grammar is the least of my worries.

Hey...
An interesting story you got there dear...
You don't need to think about the flow mate...
A poem is also a poem if it doesn't rhyme or if it does not have a perfect flow...
Just write what you wish to don't force anything into your piece...
Keep it natural....
This is a good piece i cannot see any mistakes in it...
Keep up the good work...
PM me for anything...

I have to disagree with the previous reviewers on grammar and structure. The ideas behind a poem form its core, but the presentation of the piece is tremendously important in how the reader interprets it. I've seen brilliant poems that were all but ruined by structure and grammar issues.

As far as structure, try to break your lines in places where there's a pause in flow or a change in idea. If you break your lines in the middle of a though, the flow can easily become too choppy. Try reading your poetry out loud, you should notice places where the action lulls or you hesitate. Those are often good points to make line breaks. That said, there's no set formula, so just keep playing with things until they feel right. You'll get there.

It's also a good idea to break poems up into stanzas so that readers aren't intimidated by a huge block of text. Stanzas are usually broken up based on changes in idea or perspective. If you aren't sure how to break a poem up into stanzas, try putting lines with similar tone and angle together. It can also be helpful to have a general layout of the poem in mind before you start writing. This usually gives you nice, even stanzas, but you have to be careful not to force things.

As a general rule, you want to keep your rhyme scheme consistent. Having a constantly varying rhyme scheme can be distracting to readers because it makes them stop and figure out what you're trying to do. Again, having a plan of what you want to do can be very helpful.

Capitalization generally works in one of two ways:
1. You capitalize the beginning of each line
or
2. You capitalize normally, as you would in a paper or story.
It's usually best to choose one way and stick to it. Like with the rhyme schemes, consistency keeps the reader from having to wonder what you're doing.

I can't help you a ton on grammar, as I'm still learning how to use it effectively myself. Grammar in poetry works fairly similarly to grammar in other pieces of writing though, so if your grammar works fine as prose, it's probably fine as poetry also. However, I do tend to see it more frequently used as an effect in poetry.

Now to actually review your poem

You have some nice ideas here, but it feels more stream-of-consciousness than poetry at the moment. Try working in some imagery to balance out the emotions and thoughts. If the reader can picture what's going on in the poem, it will be much more effective.
The second line felt a bit awkward to me. I really like how you use a physical aspect to make the girl more like an object, but as breasts tend to come in pairs, "just some breast" threw me off a little.
For a large part of the poem, the writing is also very similar to how someone would talk. Try using some metaphor or imagery to make things more poetic. Reading as much poetry as you can is one of the best ways to better understand how to use poetic language to enhance your poems.
You have a good start here. Keep practicing your poetry and I guarantee that things will get easier and clearer

Don't focus on it while writing. Just write whatever comes to mind, and if necessary, make small changes. In the meantime, read other poems and learn a bit about the different types of poetry. In time, you will begin incorporating the little things into your poem. Don't ever think too hard about it. You want it to be fun, not a hassle.