Belly tightening

Selena πŸ₯° β€’ πŸ‘ΌπŸ»πŸŒˆπŸ€±πŸ‘ΌπŸ‘ΌπŸ€°|31

Every time i go for a walk my belly gets hard/ tight and extremely round. Why does this happen? What does this mean? Does the baby not like walking time or are they contractions? Im currently 6 months.