We all jump to the conclusion or thought that something really bad is happening, but the odds are that it is not.

Your Dr has suggested stress. Have you discounted this? Having this headache will cause you stress, so it must be a factor.

My 25y + headaches, stress related, were eventually tracked down to very tight neck and shoulder muscles.

Stress from doing too much PC work, plus working to a high level and not pacing myself.

This was diagnosed as stress a long while back but there was no treatment offered, except a strong muscle relaxant, which i declined to take.

Far too long later, I found remedial massage relaxed the muscles and the headaches stopped.
Came back of course so i continued with massages for 2 years.

Now I take magnesium and that has stopped them almost entirely.

So give stress and tension a good looking at, I'd suggest.