Parshas Ki Teitzei - Kiddushin with less than a shaveh pruta, a yevama marrying someone other than the yavam and the pnimiyus of eishes yefas toar. At the end there is an article on the topic of thinking about Torah and the existence of Hashem in unclean places. I direct you to an EXCELLENT sefer that discusses [among many other things] this topic.
Rav Shlomo Einhorn - מעשה חושב