Mid cycle bleeding pic included

Okay so I'm 12 days out for af so I'm pretty sure I'm noting getting it early . And way this morning started with some light spotting and just I got a pretty good amount of blood . I don't think it's implantation because my doc said my tubes are blocked and my chances of getting pregnant unassisted are like slim to none . Any one have any ideas what else could cause this .? I am cramping and I feel like I'm dragging .