af?? but doesn't seem right?

Samantha
Hi all. New to this. Af was supposed to come today. But no sign. Did a test. Got a bfn
Just went for a wee and when I wiped I thought af had arrived, but when I looked it wasn't right. It's usually blood red. But this is a kinda brown colour?? I have herd of implantion bleeding, but isn't it to late for this? 
Thanks in advance for any advice. X