Hi hun, actually 15 weeks is still quite early, some mummies don't feel the baby bump or that firmness until later, especially if this is your first pregnancy or if your uterus is tilted backwards (which is totally normal!). Setiap pregnancy is different, so don't worry too much, but it's best to mention this to your doctor at your next checkup just to be sure everything is progressing well, okay? They can do an ultrasound and put your mind at ease.