My son is 6 weeks old. What kind of developments should I be looking for? He is starting to track people with his eyes. He hasn't shown any interest in any toys on his play mat or car seat. He is gassy smiling but not reacting to us at all yet. I just don't know when I should expect to start seeing those developments and when it gets to a point where I need to speak to my pediatrician. I am not concerned or anything, I just want to know when to look for those things. Also, when did your baby hold their head up unsupported?