I feel for you so much. So incredibly frustrating when we're left to wonder what's 'wrong' with us, as opposed to being inspired to find the natural reasons behind why things are feeling so wrong.
I'm 'Mum' to a 15yo daydreamer with plenty of energy and a longing to express his creativity in non boring ways. Things have become so incredibly frustrating for him to the point where we're now part of the way into our quest for ways to manage such an incredibly amazing and sometimes frustrating nature.
Dietician suggested somewhat of a protein deficiency, given that proteins are the building blocks for basic function (regarding mind and body) and his diet has been lacking. So, more protein has been introduced, along with a good brand fish oil with omega 3 DHA etc. The most recent thing we did on this leg of our journey was consult a GP who is an absolute legend, not dismissive like most people, who tend to put my son's struggles down to 'just being at that age'. He's truly done with hearing that line by the way. Such dismissive opinions were beginning to contribute to him heading toward pure hopelessness and depression. I've dealt with depression in the past and know the signs. Anyhow...
The GP recommended a psychologist, as a way of looking to what could be behind the lack of focus. Spoke on the phone to the psyche (to make an appointment) and she suggested appointing one of their neuropsychologists as being better match. GP also mentioned that while daydreamers are the natural entrepreneurs, inventors and theorists in life, while the daydreaming part of the brain is important to exercise, there's a problem with it being accessed too much. While it's being exercised, the part of the brain that is more about focus isn't being exercised. It becomes about an imbalance. He recommended the app from the 'Smiling mind' website, which addresses creating a balance.
Another factor we're working on is 'How to manage what's boring'. I know, sounds a bit weird, as why should you have to manage what's boring in life but sometimes there's no choice. One thing he found that makes a difference comes down to venting the excess energy that naturally comes about for him, so he can let go of it long enough to help his focus. He runs.
Basically, we're on a quest to help him master his natural abilities and find skills in channeling his focus. Again, it's tough when no one seems to get you but when someone does, it's life changing.
Go for that second opinion.