weaning symptoms? PMS?

SKD • Lost my baby girl at 20 weeks February 2015. Rainbow baby boy born January 20, 2016🌈👶🏼. Early MC May 4, 2017. Second Rainbow baby boy born March 18, 2018!🌈👶🏼 💗Shayla Rose👼🏼💗 💙Royal Holden👶🏼💙 Lucas Stephen 👶🏻💙
Hey ladies!  I completely stopped nursing July 20th, but I was supplementing since July 1st.  I've had what feels like menstrual cramps for about 2 weeks now. Any ideas if this is the build up of AF or something else?  I did not get a period yet and I took a pregnancy test two days ago and it was negative.  My lower back is achy too😕.