Implantation bleeding

I'm not sure what to think of this , so hoping I can get some clarity...

Yesterday morning I took a shower and put on a small panty liner. I felt super wet and noticed that I had a ton (like it felt like urine) of CM with a little pink color on liner. Decided it must be period and changed to a pad, since I was 100% sure. Period is due on Sunday. For the next 3-4 hours I had red blood. After those hours, I had nothing else on the pad or when I wiped. Is this implantation bleeding? I have another child, but this didn't happen with him. Thanks!!