Hi Macksmom,
first off, I wanted to let you know that I edited your title for clarity, I hope... although maybe I made things worse, because the term is so commonly misspelled, lol! :roll:
:explanation: "Palpitations" are abnormal heart beats; hard, fast, irregular beats, and/or pauses. When feeling for kits, we are "palpating" the abdomen.
Now, to your question- you are kind of past the window of easy palpation. It is normally done between the 9th and 16th day. At this stage, the kits are not as well protected by amniotic fluid, and I have found that somehow they tend to "hide" in the abdomen. I have been fooled more than once when trying to feel kits at this stage.
As for her behavior, you want to place her on your lap or a table, and gently press her head down. Then you will reach under her and gently squeeze up high under her loin muscle. Your fingers should nearly touch through the walls of the abdomen. You then slide your fingers down until you feel something (or not). In the earlier stages, the kits feel like firm but squishy grapes. Now they will probably be more elongated.
If she tenses her abdomen, take a break and just pet her until she relaxes and then try again.