If everything was okay during the 20 week detailed scan, there is no need to worry at all, mummy. Most first time mums start feeling baby's movements between 18 and 26 weeks. For some mums, feeling those first movements may take longer than others. Maybe you have already felt your baby move but did not recognise it. The first movements of baby will usually be like flutters or bubbles popping. As your pregnancy progresses, and your baby gets bigger and stronger, you will start feeling those kicks properly. Also, if you have an anterior placenta, you may not be able to feel baby's kicks and punches much. Another reason you may not be feeling your baby move yet could be blamed on the position your baby is lying in within your uterus.
You can do kick counts at the same time everyday. It's good to consult your doctor anytime you are in doubt