When's best to take test??

Rachel
My period was due today but glow said to take test two days ago so have everyday since but all negative including today. Still no period and don't feel like it's coming. I had a missed miscarriage April 2014 and been trying to conceive since with no luck. I have an ovarian cyst which they say is massive but having an op in September and also a dye test. Any advice would be great. Thanks xx