Has anyone else experienced this..?

I’m 25weeks and 4 days.. I just saw a specialist for another ultrasound because my son is measuring small. My 20 week ultrasound he was in the 17th percentile then at my 24 week ultrasound he was down to the 13th percentile. My last appointment they were concerned with him being so small so they sent me to get another ultrasound. Today he is now in the 10th percentile. Has anyone experienced anything like this? I’m just trying to ease my mind, I don’t understand and I feel like I have a million questions I don’t even know what happens from here...

thanks I’m advance