I'm 15 weeks too and I don't feel pregnant at all either. I don't have any morning sickness or any other symptoms and I'm not showing at all. But don't worry! The app even said when I got to week 14 that I might not even feel pregnant so it's completely normal :) I heard a strong heartbeat a couple days ago at the doctors so I'm just remembering that to keep me going. Don't psych yourself out! Miscarriage is very low when your in the second trimester. You'll be okay but I'll pray for you too :)

Personally, it never hurts to call your doctor and tell them they you're worried. Usually they will have you schedule an appointment and use a Doppler to check for heartbeat to let you know everything is ok. If they can't find one they will wheel in their portable ultrasound or have you schedule an ultrasound to check on everything. In the second trimester the placenta usually takes over and you lose a lot of your pregnancy symptoms. It's pretty normal to feel more normal during the second tri that's why women tend to like it better than the other trimesters. But if your really concerned call your doc or midwife and let them know. They should take care of you.

I'm glad I'm not alone. 15+3 I still have morning sickness but I keep psyching myself into thinking it's all in my head. I'm still not gaining weight, but working hard to eat and drink plenty.