Yesterday when i was out and about with a friend... he offered me a cigarette... the only thing those was that there was a condition... i had to have sex with him... i said no... so he left it at that... then he some how slipped some into my bag... with a comdom and left a note... saying... just in case you change your mind

i am happy with my girlfriend
and this guy is my friend...
so what should i say to this guy without loosing our relstionship... but without loosing my girlfriend... i wont do anything which will harm her... but what should i say to this guy??? which wont harm him...