Please call your own doctor now. He needs to know EVERYTHING you have done, medicine doses, pedialyte intake, wet diapers a day, what your child is eating, etc. He may want you to bring your child in to see him so that the croup does not turn into something more serious. Or he may just give you answers over the phone. My doctor's nurse takes all my questions and gets back with me with the answers in a timely fashion every time I call.
Make sure you have all of your questions written out in detail before calling. Leave plenty of space on that paper for you to write the answers.
Ask about hot water vaporizers (about $12 each at Walgreens)which you can add 'menthol liquids into the water' versus cold water vaporizers (much more expensive, many varieties available-get one with inexpensive filters!!)
Standing in a closed bathroom with the hot water running followed immediately by going outside into the cold night air was recommended by 2 different doctors for both of my boys (we moved to a different states and still was told this solution for night time hacking).
Ask about using plug-in menthol dispensers (about the size of the palm of your hand).
Elevate the head end of the bed (using rolled towels under the sheet to 'build up' a ramp to put his pillow on. My little guy was still in an infant car seat and slept in it to help keep him upright and decrease his hacking.
They might give a steriod shot to help decrease the constriction of the airway.
How much tylenol vs. motrin to give (make sure you have a current weight for dosage).
Ask about what to feed him and drinks to give. Pedialyte was recommended over Gatorade for kiddos by my doctors.
Good luck and make sure YOU rest when you can too. Croup wore me out every time my 2 boys had it. Call you own doctor when you have questions.