YOU SAID:

I'm doing this I guess

INTO JAPANESE

私はこれをしていると思います

BACK INTO ENGLISH

I think I'm doing this.

INTO JAPANESE

こんなことをしているんだと思う。

BACK INTO ENGLISH

I think this is what you're doing.

INTO JAPANESE

これがお前のやってることだと思う

BACK INTO ENGLISH

I think this is what you're doing.