Nikov,
I was introduced to photoreading towards the end of my medical school. I understand your overwhelm with trying to know everything in your medical school studies and especially for the boards. I am currently an ER resident and always use photoreading and activating with my textbooks. I was introduced to photoreading at the end of my medical school.
I think the biggest thing I can share with you is the importance of getting the big picture first despite all the technical details. Get the big picture with previewing and photoreading. This forces you to go through the material several times over with activation, each time adding more detail to the overall picture. Remember, do not reading every single word with activating. There's a great temptation there especially with technical details. There's a lot to cover, but you can do it efficiently. I understand your stress. But as you know, it's really important to be as calm as you can be - this enhances your learning. The amount of time you take to learn a subject matter in high stress level states can be double the time you take to learn the same material in stress-free states. I've been amazed with how much I retain when I'm in the alpha brain wave state.
Understand that your method of activation will be different with more technical books than with regular reading books. I have different successes with pleasure reading books than I have with medical textbooks. With medical textbooks, I do rapid reading and know exactly what I need to pick out. Set your goals for what you need to get out of the material. Once you try to relax yourself with counting down or deep breathing, tell yourself, "I am curious to see in how many ways my mind will notice all the pertinent information I need for the boards" or something to that effect. Remember to ask yourself mind-probing questions even as your activating. You WILL find the answers. Remember, with photoreading, one month is plenty of time to study for the boards.
And remember, the boards are not going to ask you every single detail in your books. That's why photoreading and activating will help you center in on the pertinent stuff as long as you set your goals and purpose.
But please do find ways to calm yourself down. Find what works for you. This is good investment of time. This is real key.
Good luck!
-Krishna