4 days late, BFN..will this mess up next cycle?

Feel like my body is betraying me. I’m 4 days late and 15-16 days PO. I had mild cramps the whole two weeks so thought for sure I’d get a +..I’m never late and now it’s 4 days with nothing. I can come to terms with the BFN bit now I’m wondering if my cycles all messed up? My usual fertile window would start in a week but with no AF, that doesn’t sound like a healthy time to ttc. Thoughts??