My near 8 month old (in a couple days) has no interest in crawling. He rolls around, but gets super frustrated if toys are infront of him and instead of trying to grab them he just crys. I normally just let him go and he eventually stops and plays with something else. He also crys hysterically when I put him on the ground laying down. He only wants to sit. Is this just a phase or could something be bothering him? He also doesnt have any teeth yet? Not even showing signs of getting any? I feel like hes a far bit behind his cousin who is same age and has been crawling for a month and has 2 teeth 🤔