I have no experience of implantation bleeding myself but I've know quite a few of the TTC girls thinking they were out of the running when they started bleeding and some have even said that their bleeding was heavy enough for a period and yet they were still pregnant.
I can comment on the pains though as I had awful, awful pains at 9, 10 and 11dpo - I was convinved AF was on her way only to get a BFP at 14dpo. The pains were probably as bad as the worst AF pains I've had, so cramps aren't necessarily a bad sign either.
I really hope to be reading your BFP announcement soon 