feeling nervous

Hey guys! I'm currently 17w3d and I've really been struggling. I had a mmc last August at 8 weeks. This time I've seen the heartbeat at 7&9 weeks and I've heard it via Doppler at 11&15 weeks. Lately I've been very nervous and anxious because I don't have a bump, I can't feel my baby, and have no idea how my uterus is supposed to feel. I'm worry when I go in for my 19w ultrasound something will be wrong. The doctor told me at my 15w that we've heard the heartbeat and I have nothing to worry about, but it's almost like o can't believe her, and I second guess whether whT we heard was actually a heartbeat.