weird period

Sarah • 25 yrs old mommy of a beautiful baby girl!👶 God bless every woman who is trying!😍😘 much love from this mama

Okay so I was suppose to start my period the 20th but didn't till the 22nd but I'm spotting then off and on again? What does this mean? normally this don't happen....i thought I was pregnant but took the test the 21st and it was negative. it's been almost 3 weeks since I had unprotected sex so could I be or what?! has this happened with anyone else??