Low fetal movement

Annabelle

So as a backstory to why im freaking out, i went to the hospital for a fall last week at 23 weeks pregnant. Baby was fine, extremely active, but they couldnt find the heartbeat. After them starting to get worried, i showed her where his heart would be based on what I was feeling and they found it right away. They advised me to start doing kick counts because I have a high risk pregnancy, even though it was a few weeks before most people start them. I've been doing them for the past week now and have had no issues until now. He hasn't moved in over 3 hours and I am so paranoid since I usually feel most of his movements, even though Im 24 weeks. Should I be worried that its been over 3 hours now? This is baby #4 and this never happened with the other 3