Here is one description of palpating:
"Hold the ears and the fold of skin over the shoulders in the righthand; place the left hand between the hind legs, slightly in front ofthe pelvis; place the thumb on the right side and the fingers on theleft side of the abdomen; exert light pressure and move the fingers andthumb gently backward and forward. If the doe is pregnant, you shouldbe able to distinguish the embryos as marble-shaped forms as they slipbetween the thumb and fingers. Handle the doe gently, and use onlylight pressure on the abdominal cavity. Accurate determination ofpregnancy by palpation takes practice. If you are inexperienced,repalpate does diagnosed as nonpregnant a week later. If a mistake hasbeen made in the first palpation, the doe can be put on a full rationand provided with a nest box at the proper kindling time. Withpractice, you may develop enough skill to diagnose pregnancy as earlyas the 10th or 11th day, but that will take a lot of practice."
(As a suggestion...if you have two does, one who definitely isn't pregnant, you could try palpating the two and compare.)
I used to try palpating when I raised Polish years ago, but neverdeveloped the confidence to do it accurately. However, I also didn'tbreed my rabbits very often, so didn't get to practice it too often...