Got my bfp or not! confused?

Ok too make a long story short we have been trying for two years I haven't ever had a test say positive except for 3 years ago wit my first, well my grandmother said I lookd prego so I went and bought a test cas she knew last time I was and sure enough it was a BFP , well tested twice this afternoon and both negative???? Maybe diluted pee or what? Need advice!!!! Babydust ladies!