if you like rhyme, make it work for you. There are going to be more than a few people that will tell you that rhyme is old fashioned or passe. Yet, in the fifteen years that I have been around writing, I have seen many new rhymers. I feel that rhyme is kind of like a drumbeat; it helps to keep the tempo and you vary the beat to suit the rhythm of the story. I sense a rap background here and it may be very useful in your work. Read lots of poetry, listen to lots of music. I would have cut the first line of the last stanza in half and given the last stanza a fifth line and done it like this.

"when I was fifteen and started to write
I couldn't wait for the rain
for some reason when it rains, I'm no longer in pain
and I can write
I'm like a bird that's taken flight

I think that this can be made much smoother, but you should leave it and come back to it after a while with fresh eyes. Say it out loud to yourself, with the beat that you imagined as you wrote it.

~ Geezer.
.

I have been accused of rhyming a bit myself. This poem is a good display of emotions. But I think you have tried to pack too much into the first line.Now on to the last stanza. I am myself guilty of varying line lengths too much so I recognize the same in others. This would read a bit better if you tried to make the last stanza's line a bit more uniform in length . something like :
When I began writing I prayed for rain
For all the drops washed out my pain
leaving my heart free to write
like a bird on its first flight...........................this is just to show that there are ways to do this and is not to be taken as word for word instructions. I will be pleased to see the final form you come up with