I definitely had an implantation bleed when pg with DS1, albeit it was 4 years ago and my memory sux ...

When did it start? Couldn't honestly say as my cycles were out of whack, but I was on second cycle of clomid - I "think" it would have been approx 8-9 DPO.
What color was it? Red-brown I think.
How long did you have it? Only remember it being 24 or 36 hours at the most - enough to make me think AF was on her way soon.
Did you have cramps/back pain? No.
Did you have any other symptoms with it? Nope, but I do remember there was very little blood all up - literally was a tiny bit of spotting throughout the day.

Good luck N2L - I hate how when you are LTTTC your body plays tricks and mind-games. Hope it all leads to a BFP for you though!