Can you spot earlier than around your expected next period?

mommabear
Okay, so my question is can people have spotting before their expected period (the time around when they should spot)? 
I read on some websites you spot around when your period should start. Some say it's 6-12 days after conception. 
So, here's my last few weeks: 
Oct 3rd: unprotected sex on a fertile day 
Oct 7th: projected ovulation day
Oct 9th: spotting (lasted maybe an hour) 
From Oct 5th until today I've been having: nauseous, moody, emotional, bloating, bad cravings, having cramps everyday, tender/sensitive nipples, creamy white cm, high and soft cervix position, etc.
My next period is due in 6 days (Oct 21st). 
So, was that spotting or implantation bleeding? 
If I conceived, I would only be 3w5d (per glow app
(Ps: I took a Walmart "first signal" cheapie test and it was a negative. But I've heard that they aren't good with detecting early pregnancy. Does anyone have any experience with those?)