Your story reminds me of a great quote from Hamlet: "There are more things in heaven and earth, Horatio, Than are dreamt of in your philosophy."
What I mean by
this, is that head pain after stroke is a fairly common problem, but it has never been clear to me (and to other physicians I have discussed this with) why it happens so often. Provided any dangerous anatomical reason has been excluded (such as brain swelling, vein clotting, arterial tear, etc.), most of the time the cause is not obvious. Please try to take comfort in the fact that this does happen to many people after a stroke, and if your MRA/I appears normal, you probably have little to worry about.
Also, I would not use the term TIA to describe this. In general, I think TIA is probably the most overused diagnosis in medicine, and refers to a very specific rare type of ischemic cerebrovascular event. It does not sound like you are having TIAs.
What often helps these pains are medicines used to "dial down" pain neurons. I have had a lot of success with older anti-depressants (called tri-cyclic antidepressants) and some newer anti-depressants (namely duloxetine). Other options include anti-seizure medicines such as gabapentin or pregabalin. Alternatively, you could simply try more standard pain medicines such as Tylenol or Ibuprofen.
I hope that helps.