Im 39 weeks and last visit i had with doc he said that the hard bump was a sign that baby was measuring big. Idk what it can be in ur case since ur only 4months but when u go to ur doc visit ask if ur belly is measuring correct. So u can avoid a baby too big at an early time in ur pregnancy
I'm 19+2 and every morning my stomach is super hard and once I get up and move around it goes back to normal hard and not a balled up knot lol
Where does the baby do it at? Lower abdomen?
Probably the baby balling up. Mine does it constantly.