Need answers please...

I am (by glows calculations)10 days late for my period. I'm showing many signs of pregnancy. 9 days ago I experienced what I would have SWORN was implantation bleeding. I have a small group of people who I chose to tell about my suspicion that I may be pregnant. Every single pregnancy test I've taken comes back negative, but I honestly just don't understand how I can't be pregnant. My support group is beginning to think I'm desperate and ridiculous which isn't the case. I AM patient! But who can tell me about their experiences. Has anyone ever taken test after test after test getting negatives AFTER a missed period only to find out that they were ACTUALLY pregnant. How long did it take for your BFPs to finally show up?