Sorry to hear it.
Here in the US, your school district may have an audiologist on staff who should be able to consult with you, give you another opinion. Large districts sometimes have a full-time person, smaller districts sometimes contract out for these services.
Depending on the size of your school district, there may also be a good Deaf and Hard of Hearing Specialist who should see lots of kids and can help you learn the ropes, or refer you to a parent's group for DHH kids, or at least give you some names of other parents who've been through this with small kids.
The speech and language specialist at your son's school should be able to point you in the right direction. You may also want to have them screen his speech to see if there's anything you need to address.
Here in CA, our medical insurance also has a pediatric audiologist. It sounds like you may need to consult more with them about your options. They should also know about local parent groups.