I got a positive pregnancy test same day my period finished next day i did another one and it was negative what can this be ?

Possible: Very often women experience biochemical pregnancy that are detected by doing a pregnancy test. However, when the test is repeated, it comes negative. When the sperm or egg union is not perfect, conception occurs but the pregnancy does not grow. One experiences a normal period which may be slightly heavier or slightly delayed by a day or two or patients may get heightened symptoms. NORMAL.