Could i be pregnant? Im giving up hope!

Well i was due on on Friday and i still havent come on , i got my hopes up, did a test this afternoon and a BFN !!! Could it still be too early to be detected or am i just kidding myself and my periods just simpy late?

I had cramps on Friday, thought my period was coming but it never did, my breasts feel tender but not as sore as they have in past months..but im full of spots, and about 10days ago, i was out shopping, i got this really bad pain in the bottom of my back, was so painful i had to sit down, once i did i got very hot and thought i was going to pass out but didnt..could this be a sign??

Please any advice would really be apprieciated..whats the longest someones kept getting negatives before they got a BFP when they knew they were pregnant? xx