11pdiui

I am currently in my tww from my first iui. On Sunday (9dpo) I had spotting when I wiped. I wish I had taken a photo of it but I didn't have my phone with me. It was very light and pink/brown color. Only there for one wipe and nothing since. I have had lower back pains off and on and mild cramping since 8dpo. Today is 11dpo and I tested this morning but it wasn't first morning so it was bfn. Could that have been implantation spotting and I just need to give it a few more days? Anyone else have anything like this?