Cannot get into macos after bootcamp in window 10

When I first hold option after rebooting I was able to get into macos without problem. But after that, I constantly tried going back to the startup thing again and again where I was able to get into my macOS on my first time, there's no Macintosh HD popping up and I cannot get back into my macOS where all my work and programs are installed there. I only wanted to install window to play some games, but I regret my decision.