I am in the same dilemma!! I let DH "stay in" because I was at the end (CD6) of AF and I figured... What's the harm? Well I started spotting on CD16 and am freaking out that it may be implantation spotting!!
~ a little background ~ DS weaned himself from BF @ 12 months (AF returned at 6 months PP and averaged about 55 days long... I've always had long cycles) So we have not been BFing for 4 solid months. Prior to most recent AF I had 3 days of spotting (very light usually only while exercising, starting on CD 28), then I went on 28 more days until the real "AF" showed up. Now I am day 18 and still spotting... And I never spot this soon after AF... But it is within the 7-10day implantation spotting "window" YIKES!!
I know you can get pregnant on your period if you ovulated early, which is entirely possible if you are irregular. Hugs~ good luck!!