You are asking what happens to the sperm that is left if it is not 'the' sperm that impregnates you? First, sperm can live for around 5 days in your reproductive tract because of the mucous there. If you have sperm that has fertilized the egg, what happens to the rest is your question? It moves around your reproductive tract and then disintegrates. Live sperm fertilizes an egg. One sperm fertilizes an egg unless yo are having twins in the case of one egg, two sperm but that is very rare.