You are asking one of the deepest questions that the Rishonim discuss. Basicly, the world exists on two dimensions. One is from our perspective, one is from His. In our perspective there is total bechira, with nothing dictating our choice.
There is another dimension to existance, that transcends our understanding, in which we don’t really exist, we are merely expressions of His Unity. In that dimension, He knows our choices. However, just as we can’t fathom Him, we can’t relate to such a concept of existance,
Rav Aryeh kaplan compares it to seeing the same thing from different lenses of eyeglasses.
As I said ealier, the Rishonim (see Rambam in Hilchos Teshuva) say this is a most difficult concept to understand.
Bottom line: to the extent that you exist the way you think you do, you have complete bechira. Use it wisely, and reap its rewards!