Chances of me being pregnant?

I know I need to wait for the first missed day of AF to do a pregnancy test, but as I can't think of anything else I thought I would ask what your experiences were and what you think. I have 35 day cycle and bd'd around the time I believe I was ovulating. AF is due on 23rd and on Friday just gone there was some very slightly pinkish discharge when I wiped (sorry for the TMI). It was enough to make me look twice but not enough to worry me and it looked nothing like AF Across Friday and Saturday I had PMS style cramps (although it's too early for AF) and lower back pain. Today all of that has stopped and I am just wondering if this might have been implantation? I don't recall having this with my first child, but then I wasn't really looking for the signs at that time either. Does this sound like implantation to anyone who has experienced this before?