the story was bassically in my head before finding the jam,i changed the perspective a bit and planned out how the story would go and how the gameplay might be,is it too much it seems like it

I think it's alright to plan for the jam, just as long as you don't start working on the game itself (programming, art, audio, and so on...), you should be fine. 

I could be wrong tho, this is all based of what they said in their FAQ: " Submissions for the jam should be original. Most of the game should be created during the jam. Games made specifically for the jam are preferred, but other games are accepted if they comply with the rules of the jam and timeframe. ".

I'll assume "most" means planning before the game jam is allowed lol. Also, since there's no concrete theme, planning should be expected. Again, could be wrong.