Hello,

Do you know how to say:

"I have so much homework! What a pain (in the butt)!"

...in Japanese?

No?

Okay, well here we go...

「めっちゃ宿題あるねん！スゲーめんどうくさい！」

Here is the breakdown:

めっちゃ= This is the Kansai dialect 「関西弁 （かんさいべん）」 version of とても, meaning very (or "a ton"--as in this case) 
宿題＝しゅくだい=homework
ある＝This is the dictionary form of あります, meaning to have.
ねん＝This is not 年（ねん=year), it is again from the Kansai area. It is like よ （I think), like あるんだよ　which adds emphasis.
スゲー = This is the slang for すごい, which means：terrible, great, amazing, wonderful, dreadful
めんどうくさい  ＝ This means: a pain, or pain in the butt. But the dictionary will give definitions of tiresome or
bother, bothersome. And it means that too, but it can mean "pain (in the butt)"--because it's saying the same thing.

Okay, so if you want to know the standard Japanese version (not Kansai Dialect), then I think I would say something like:

「ちょうしゅくだいあるんだよ！スゲーめんどくさい！」

Got it?

Cool!
Have fun using it.