Every baby achieves milestones at different months. What you are seeing is only 1 of the 5 aspects of milestones i.e gross motor. There is fine motor, language, social, sight and hearing assessment. Only a pediatrician can assess growth in all these aspects then decide whether there is a delay or not.
Next Steps
As of now, please be patient. Give your baby some time, he will start crawling soon.
Health Tips
visit pediatrician if you want him to be assessed.