Ladies ?

Ok ladies, lately I've been experiencing this small bump on my right side more when I lay down flat upwards some times not all the times. I remember having this same feeling when I was pregnant from my son, but I'm concern cause my periods been irregular, I can't be pregnant. cause I've taken 3 pregnancy test and they all came back negative. Any opinions can it be something else? I've been feeling discomfort when I lay flat on my stomache just to mention sometimes I feel fluttering/popping sensations on my lower abdominal