Perhaps yours is a problem with posture. Have you tried a neckstrap, or raising or lowering the peg? Or getting someone else, preferably a recorder teacher, but perhaps anyone, to look at your body position while playing? The mouth piece, instrument height etc. should adjust to you, not the other way around.
Also perhaps there is some tension or too much body stiffness while playing? A second set of eyes might be helpful.
Good luck!