12 Days Late No AF All negative tests... ANY THOUGHTS ?

Hello anyone can help me whats going on ? My period is late by 2 whole weeks well 12 days to be exact... which is unusual for me.. im currently 13 month pp & ive been having regular cycles before & after my 1 year old... im confused... i did urine & blood both were negative... but i think im still pregnant or something isnt right! Lol any thoughts ?