At 20 weeks, the movement I felt was still very subtle. I had to really be paying attention to feel it. Around 21 weeks, the kicks started getting more intense and after 23 weeks, I definitely notice. For some women, it can be normal, especially if the baby is facing toward your spine. Or do you know if you have an anterior placenta? That definitely affects when you feel movement. I'm sure you're fine, but if it's worrying you, definitely bring it up with your doctor.
But I do know at 20 weeks, I had my ultrasound, the baby was kicking during the ultrasound, and I didn't feel it at all.