Total opposite pregnancy

Everything about my second pregnancy is different! I'm 18 weeks 5 days but measuring a week early my ob had told me. I'm kinda freaking out because with my first she was kicking all of the time around this time and I never feel this one , like ever . It's starting to scare me a little bit, I think I'll feel her but then. Idk. With my first daughter it was clear I knew it was her. The last ob appointment it took a while to find her heartbeat because the doctor said "woah she's way back there" so maybe I can't feel her as much because she's in my back more? Idk. Kinda scary lol