Girls, can you tell me if my uterus is getting smaller (from just belo…

Girls, can you tell me if my uterus is getting smaller (from just below the belly button to slightly below the breastbone), then it becomes normal, then I feel a slight pull in my lower abdomen, then it lets go, the baby moves around, kicks, is that normal? There are no discharge. Could it be because the baby turned so much? Or something serious? Several times a day like this