What Causes Feeling Of Air Filled In Ovary Or Fallopian Tubes?

for a few weeks now, I have had movements that resemble pregnancy. I should know these feelings, since I have had 5 children. I had my tubes tied, and half of them removed after the last one. I shouldn t be able to have anymore children. a few weeks ago, more like a month or so ago now, my period was two days late. I took a test. it was negative. when my period did come it only lasted three days. this has happened two months in a row now. Ive taken test and been to the doctors. they can find nothing. now I have another symptom. I feel like I have air in either my left ovary or the tube. And once and a while my stomach will jump as if I am being kicked by a bay. all test are negative. what could this be?