Is it possible for a girl to show symptoms of pregnancy within 2-3 days after having sex? Also – is it possible for a girl to seem like she’s having symptoms but.. she’s not really….? I mean – the day after I had sex, I was extremely tired and I had neck and back aches. But – the night before the aches and tiredness, I had slept at my dad’s house, therefore I slept in a different bed than normal and had gotten alot more sleep than my body is used to. Could that be the reason I was so exausted and hurting? Or could these things happen over stress? Because although I have been trying not to, I have been stressing over the fact that I don’t know whether I am going to be pregnant or not.