What Causes Back Ache And Fever After Taking I-pill?

hi.. i am 21 year old and my boyfriend is 31.. last week 7-8 days after my period stopped, we had an unprotected sex.. i took ipill before 73 hours but that same day we had sex again.. he said he didn't drop inside but still i am tensed.. this morning i was feeling kinda sick.. my back aches and my tummy feels weird.. i feel little feverish too.. please help.. my i pregnant??