Bump pains

Hey ladies I’m 21 weeks with our 3rd baby

My youngest is 5 and he’s very lazy to walk so i carry him sometimes. To be fair he’s a small 5yr old that wears clothes for 2 yr olds so he’s not heavy at all.

Lately when I pick him up I get a sudden sharp pain almost like something cracked on my bump always on the top part of the bump sometimes on left side and sometimes on the right side. I completely forgot to ask my midwife and now won’t see her for another 8 weeks. Any idea what this could be?