its very normal not to have felt any movement at 18 weeks
Don't worry, most ftm's don't feel baby move until about 20 weeks. I was 19 weeks the first time I felt my baby girl move but didn't start feeling her move a lot until about 21/22 weeks
My midwife said its normal to not feel consistent moving until 24 ish weeks. Baby is still small. My first baby i didn't feel at all until 22 weeks and she was just fine. This time I'm 33 weeks with a healthy baby and i would go several days without feeling much of anything before i was 24-26 weeks. It got more consistent after that. I know a lot of people get a fetal doppler for at home and some piece of mine. Good luck! I bet baby just changed positions and now you can't feel much.
It's hard but don't start stressing just yet. I didn't feel anything until the end of my 18th week. Even then i had to be laying down and really concentrate to be sure if I was really feeling my little hamster. I've read sometimes ftm don't feel anything until after 20 weeks.
Also if u have an anterior placenta it cushions baby movement and makes it harder for u to feel I had one with my last baby and sometimes I would go days when I was 31 weeks with out feeling her and when I would go to er everything was fine and u could hear here moving on the monitor