15 days late!!!! Help!!

Hey all I am 15 days late with no sign of af at all except some cramps on and off getting bans was at the docs 5 days ago got a bfn I'm back again this Monday for another test I hope I get my bfp my period is normally a 35 day cycle never this late it's so weird anyone think I could be preg even with negs this late?? Advice from anyone please