Positive test 3 days before period due date and a negative the day before period due date

Gemma

Hi I tested 3 days before period due date and it was positive. The day before my period due date it is negative and it was done first thing in the morning. Could this be a chemical pregnancy or do you think it could be just a false reading due to hgc levels? Has anyone else had any experience of this and still got a positive after?