Too early??

So when I woke up Monday morning I had what looked like dried blood spots on my knickers, got my hopes up slightly that it was implantation bleeding 🙈🤦🏻‍♀️ so thought I’d test this morning (Wednesday) but came out negative. But it wasn’t a early detection test was just a cheap one I had laying around that cost me £2 from Asda 🤷🏻‍♀️😂 so my question is would it of been to soon to test with a preg test like that? Also glow is saying my period isn’t due till 6 days, but last month I started it on the 18th witch is only 4 days away... Iv looked throw my calendar on this app and each month its putting my periods back a couple days, why is this? I pretty much always come on on the 18th so not sure weather to go by what glow says 🤦🏻‍♀️ confuseddd!!??? 😭😭 been trying for our 3rd for 2years now with 2 miscarriages towards the beginning when we started trying and nothing happening for well over a year now and getting so frustrated with it all 😔 also used preseed for the first time this cycle and obviously being stupid I got my hopes up a bit with that too 😂😭