TTC - fertile window bleeding

Hi ladies. This is my sixth mo TTC and today is the last day of my fertile window. I started some light, dark spotting this morning and now it's heavier and more red. Anyone experience this? I think it's too early/heavy for implantation bleeding and my first was a surprise so I'm not sure if I did with him. I'm getting so frustrated and now this. What do you all think? TIA. Xo!