What is a C-section uterus?

I had two vaginal ultrasound scans already and the technician said my uterus looks like I had a C-section and she was very surprised. She wouldn’t really explain much further but I am confused what that means and how it happened since I had a natural? My stomach after my first birth was always sorta weird my

lower stomach always sorta folded down and she poked the stick very forward to look at the gestational sac it actually hurt lol. Anyone have any insight into why this happened even though I did natural? I wonder if I will have complications with this pregnancy such as carrying really low. Im almost 7 weeks and still not showing anything since I am carrying very low.