Confused

So glow is saying I’m 6 days late HOWEVER last month I came on on the 4th August so today is the 4th September exactly a month after my last period today I’ve had cramps all day but no bleeding I was doing tests last week and I did one Sunday which was negative but I’ve worked it out it’s possible I could be missing a period now and not when glow originally predicted does that even make sense if I’m due on now then I haven’t come on so when would you test?