pregnant after miscarriage ?

Emma • Angle baby 24/03/2016👼angle baby 24/08/2016👼rainbow baby due 31/10/2017❤️🌈
What's the longest people left it after a miscarriage before getting a bfp before period mines been just over 4 weeks now how do I know when to test I did some not so long ago and it was negative how long should I leave it