YOU SAID:

I totally forgot I was wearing my bikini underneath

INTO JAPANESE

下に私のビキニを着ていたを忘れました

BACK INTO ENGLISH

Wearing my bikini bottom had lost

INTO JAPANESE

私のビキニのボトムを着てを失っていた

BACK INTO ENGLISH

Wearing my bikini bottoms had lost

INTO JAPANESE

失っていた私のビキニのボトムスを着用

BACK INTO ENGLISH

Lost my bikini bottoms to wear

INTO JAPANESE

着用する私のビキニのボトムを失った

BACK INTO ENGLISH

Lost to wear my bikini bottoms

INTO JAPANESE

私のビキニのボトムを着用する失われました。

BACK INTO ENGLISH

To wear my bikini bottoms were lost.

INTO JAPANESE

私のビキニを着用してお尻が失われました。

BACK INTO ENGLISH

Wearing my bikini, butt has been lost.

INTO JAPANESE

私のビキニを着て、お尻が失われました。

BACK INTO ENGLISH

Wearing my bikini, butt has been lost.