Hi @DaveB44 and welcome to the forum 
All strokes are unique to their bearers but there some basic similarities in to the all. You may find some enlighten from reading the Welcome post several of us put together of things we wish we’d been told about in the early stages of our recovery.
As we all keep saying, recovery is a marathon, not a race. Even a broken limb at our age can take over a year to recover from. Your only 4mths post stroke, they say you see the most recovery in the first 6mths. The brain needs frequent rest to give it time to heal and repair the damage done to it.
Much like you my speech was affected, I’m 3½yrs post stroke and still have a mild aphasia, but it doesn’t really hold me back 
I surrendered my driving licence after my stroke because it was up for renewal in a couple months anyway. The DVLA returned it a year later but it was still several months before I got back behind the wheel and been driving ever since.
The concentration issue will get better in time, it creeps back slow and steadily but could take anything up to a year and then some.
You could try magnesium glycinate for the headaches, apparently it works for migraines, and it worked for my headaches, but as I said, we are all different. But we burn a lot of nutrients in recovery from any major illness so it’s good to keep nutrients topped up in those initial months. Particularly the B group of vits as they are water soluble therefore cannot be stored in the body and they are important for brain health.
But its always wise to let your gp know what your taking in the event it affects any blood test readings and such
I look forward to seeing you around the forum and long may your recovery continue, onwards and upwards