My DS has bypassed crawling and is a very fast cruiser going from one piece of furniture to the other and can stand unaided for about 5 seconds. He can walk well with me holding onto one hand. He can't yet pull himself up from a sitting position, is this normal? Shouldn't he have learnt this before the walking? I am trying to teach him to get himself up but he gets really frustrated and has a meltdown almost every time I try!