Hi there
I know you are still waiting for all the tests/results to be in. Have you been started on any medication at all or are you taking anything new unrelated to PCa that might give headaches as a side effect?
MRI scans are quite difficult for some people, I have heard others complaining of severe headaches for a week or so afterwards. It is a claustrophobic environment to say the least
As you say yourself these could be tension headaches, waiting for tests and results can be very stressful I know.
If they do not ease off soon have a chat with your GP just in case.
Xx
Mo