YOU SAID:

I lay on my back and start to laugh

INTO JAPANESE

私は仰向けになって笑い始める

BACK INTO ENGLISH

I roll over and start laughing

INTO JAPANESE

私は寝返りを打って笑い始める

BACK INTO ENGLISH

I turn over and start laughing

INTO JAPANESE

私は向きを変えて笑い始める

BACK INTO ENGLISH

I turn and start laughing

INTO JAPANESE

私は振り返って笑い始めた

BACK INTO ENGLISH

I turned around and started laughing

INTO JAPANESE

私は振り返って笑い始めた

BACK INTO ENGLISH

I turned around and started laughing