THOUGHTS??!

So according to glow I am late on my period by 3 days. The last time I had sex was August 31st and it was unprotected sex. Two days ago I got a tint of pink when I cleaned myself so I thought my period was finally here, turns out it wasn’t. Its been 3 days and all I’ve had was light spotting in which ive never ever had before. I am young only 20 years old. I’ve never even heard of implantation bleeding until yesterday when I tried googling my symptoms haha... but last night I did buy two pregnancy tests and they both came out negative. I have never been so unsure about what is happening before and I just need some answers. Is there a possibility I could be pregnant? If so, why did my test come out negative? Is it too early?