I'm sorry about your injury, but welcome to NT.

Sadly, your helmet could not prevent your brain from making contact with the inside of your skull, shaving off precious axons in the process.

If you have a CT, it will almost certainly be negative. This far post injury, it is unlikely that you have something obvious, like a bleed or skull fracture, that could be imaged with that technology. Conventional CTs and MRIs are just not subtle enough to show the damaged TBI does to all those little tiny axons.

The best way to measure the impact of your TBI is neuro-psych testing. Given that you've had a number of previous head injuries, that might not be a bad idea. While you feel you're fine cognitively, a symptom of brain injury is being unable to recognize the symptoms of brain injury. If your wife is telling you she's concerned about your deficits, listen to her.

Insomnia is common in brain injury. If you tell your doctor, he/she might recommend any number of medications. You can help yourself by avoiding alcohol and caffeine, maintaining a good bedtime regime and eating properly.

You mentioned a stiff neck. Given the mechanism of injury, there is a strong possibility that you suffered a whiplash. Neck issues can cause a number of nasty, persistent symptoms. If your neck hasn't been thoroughly examined, you might want to consider that.

It really sounds to me that you are pushing yourself too hard. You can see a neuro, but he/she may well have little to offer beyond advising you to rest. With your concussion history, they could also tell you, wisely, in my opinion, to rethink the whole hockey thing. The damage from multiple concussions is cumulative. I share your love of the game, but please give some thought to the risk you're taking.