Please tell me somebody knows this song

I have had one line of a song stuck in my head for days now and no matter what I do, I can't find the song.

The only line I know or think I know is "Whatcha gonna do.......something...you"
It is a female that sings this part though and this is sort of how it sounds.

"What...cha gonna do.ooo.ooo.oooo, ........something something........youuuuuuu"

I can tell you that the "do" is long lasting, by a female artist and is done gently. By this I mean not a rough throat lyric or deepened on purpose. If it helps, I am almost positive it is a pop hit, not country. Though it is also very possible that it is a rap song and somebody like Rihanna is just singing a few lines within it, this being one. The song is also most likely from the past few years.

I hope I described it good enough for an answer, don't worry if you don't know.

Is it?
Mya - What'cha Gonna Do