The physiology of babys changes rapidly over the first few months. I think what your doctor suggested may be right. You need to teach your child that his crib isn't a bad place but rather a place which is just part of the daily routine. If you keep taking him to your bed the problem will never be solved. You have to be strong on this point.

I would suggest that when he awakes don't take him out of his crib. Let him cry a bit and then go to him. explain to him that he needs to sleep and that this isn't playing time. This will be tough for you cause he won't be happy about this new arrangement but you must stick to it.