WHATS GOING ON??

Yesterday AF came 4/5 days early, which is unusual for me as I have a pretty regular 42 day cycle. I really thought I was pregnant this cycle so I thought maybe implantation but then thought it was too heavy for implantation and it's still here today so have ruled out implantation.  Yesterday was pink-bright red and today is darker red with some brown so I think it's definitely AF but I am so nauseas today!! Why am I so nauseas?? I never get nauseas.... Could I still have a chance of BPF?