What am I feeling? Plz read

Kae • Mommy to 5 boys💙 married💚 Brutally Honest #SNS
So I'm on cd13 and been having lower andomin pain for 3 days now. CD 11 I had period like cramps but mild, then on CD 12 I had lower andomin pain and backache, and today Cd 13, I've been having lower abdominal pain all day. What could this be???
 ((My 6 year old says maybe your bones are or hurting or maybe you heb a baby in there !?! Lmao))