I'm glad you found something to help. I don't know that you need to hold it too long anyway. I think 15 - 30 secs several times a day is better than a longer period of time. I overdid Brugger on two occasions. The first was doing it two dozen times a day at the beginning, which left my overly tight left pec (my TOS side) really sore. Basically too much stretching for a muscle that wasn't ready for it.

On another occasion, I was ratcheting up the duration and the force which then resulted in spasms between the shoulder blades.

So I've learned to look for that "sweet spot" with the right duration and frequency.

Regarding the reading, I use two thick pillows, not just one. But if you still can't do it, you might try it again in a month or two or three as you improve.