My son, who is one and a half year old, still wakes between two to five times a night. we have tried everything. what is our next step?

Re-train him: If you are responding to and aiding in re-sleep rituals you are likely part of the problem. You can read to the kid as they settle, but leave while still awake. Don't rock or maintain body contact. A kid who learns to self settle will be able to resettle alone. If he leaves the room lock the door & let him know it will stay open when he stays in the room at night.