Game building takes more than hours. (Stopped at one point, no error shown)

I'm very new to Unity, so things may not be familiar to me. I have created a free roam game which is fairly big. I tried to "export" build/run. It was fine until it hit 3/5 of the progress. It simply froze. Everything is still functional though.

It stopped at: "Building scene 1: Start the game #1(5/11 Clustering /823 jobs) I left the game to build overnight and when i woke up it froze at ^

I tried again several times but the results are still the same.

Please help!