That is a good point - having his liver checked out too.
You do not say what type of meds your husband is taking, but if he is taking meds, he should be getting his blood tested for kidney and liver function at least once a year.
With regard to your question "....but why would it come for multiple days in a row and go away for multiple days in a row ....?" It is highly likely that he is getting an infection.
Have his liver enzymes checked... my friends husband had the same behavior... it was his liver
There is clearly something going on that has not yet been detected.
Has your husband been checked for out to find out if he has a cardiovascular disease and may be getting mini strokes?
The other thing that can cause symptoms like that are a kidney infection.
Not everyone will experience pain in the kidneys or discomfort on urination. But it would be a good idea to get his urine examined to rule that out. You can get him to urinate into a clear clean jar and observe his urine. If it is very strong smelling, it may be dark in colour or it may be cloudy, those things would indicate a possible infection and if that was the case he would be prescribed with an antibiotic. In the meantime regardless whether it is a urinary infection, he must drink lots of fluids and especially water. 2 litres of water is usually recommended, but more if he is sweating a log, vomiting or has the runs.
Another cause can be low very low iron levels and lacking in Vitamin B12. A blood test would confirm whether there was a problem with that.
When he is experiencing these symptoms, you must take him to the doctor to get him checked out and take a urine sample so that the doctor can check it. The best way to do a urine sample is to pee a little first, catch the middle urine flow, and finish off peeing in the loo.
When you took your husband to the doctor, did the doctor check his urine sample? If not, it would have been a good idea to have that done.
Urinary infections can come and go, but the symptoms of a urinary infection are not always obvious, but can cause confusion and affect the speech. This is because the poison from the infection.
I suggest you get your husband's urine checked out just to make sure.
Best wishes.