Berakhot 24

Can you sleep with tefillin under your pillow? Can a man do that if he is in bed with his wife? If two people are sleeping naked in a bed, can they each turn the other way and say shema? Is there a difference if it is one's qwife or someone else? What if it is one's young children? A handsbreath of a woman in a place that is usually covered is considered nakedness - to what is this referring and in what situation? What else is considered nakedness? Is it problematic of one yawns, sneezes or spits during prayer? There are contradictory sources regarding this - how are they resolved? Can one recite shema in a dirty place where there is feces or urine?