Positive then Negative

Isabella
Hi ladies, 
Did a pregnancy test yesterday morning and it advised that I was pregnant 1-2 weeks (exciting) however did a test this morning and advised (-). 
Has this happened to anyone else? 
Was suppose to have my period on 4th, however had light bleeding for under 2 days. 
Off to the doctors tonight. 
Would love to hear if this has happened to anyone else. 
Thank you 😊