We've all done it haven't we! Telling lies in bed or, to put it another way, 'Lying about sex'.
"Yes, OMG, yes, yes, yes ohhh, yes" - God I wish he'd hurry up and finish so I can get some sleep (about 70% of women fake orgasm with penile intercourse alone).
"Of course I Love you" - I've got my dick inside you haven't I. (A very common response from men to ensure a fuck or reassure a partner during a fuck).
"Yes it was fantastic for me too" - no, it was pretty darn average actually, but I don't want to hurt your feelings, maybe next time ... if there is a next time.
Sex should be a time when one can shed barriers, both physically and emotionally, and just be totally open - ideally - but in reality our inhibitions, the imbalance of the sexes or a certain element of fear (insecurity) get the better of us and we lie about sex .....