When will my belly pop??

This is my first pregnancy. I’m 18w5d and I definitely can not fit into my regular pants anymore but I feel like I’ve been the same size for a month now. I have a long torso and have always had a more toned stomach. Have been feeling baby move everyday for about 1 week. When will I get bigger?? Am I the only one that feels like I’m not getting any bigger???? When did you start really showing?