Mine got hard around 6 months when I started to really pop out. :)

I'm almost 6 months and mine is just starting to get hard...

between 6-7 months mine started to get hard :)

Same

For me I was always relly skinny and athletic and
am 25weeks now and its just now getting really hard

There are certain times when mine is hard, I don't know if it's normal! Like just now I went on a long walk, and when I got home my stomach was really hard...And i'm 18 weeks!