Help!

I really need help with this story it has been bugging me for months and I can't remember the title of it or the pairing. All I remember is that it of course is about Harry Potter and he is living with Sirius I believe. He ends up creating this animated teddy bear from an excess amount of magical power and the bear ends up following him around even at school due to his periods of magical outbursts that the bear absorbs for him. Everyone ends up worrying about his health when they discover his heart will give out if he uses too much magic. If anybody could tell me what the title of this story is or even who wrote it so I can find it again I will appreciate it and save me from going crazy trying to find it.