It’s possible to have a positive reading on a pregnancy test even if you aren’t pregnant - this is why it’s advised to wait at least a week after your period was due to have the most accurate reading.
A false positive may be because of a chemical pregnancy, where the egg is unable to implant very early on; an ectopic pregnancy, a recent miscarriage or abortion, and certain medicines or medical conditions.
It’s best to get your pregnancy confirmed by a medical professional before accepting the news to avoid any disappointment.