I had a full on phantom pregnancy last year and felt those phantom kicks. I was convinced I was really pregnant and the tests were all wrong, I wasted so much money going to doctors and even had an ultrasound but it turned out to be nothing. This really is common, though no one can give a good explanation for any of it. Relax, and believe the tests, they are not wrong. Good luck!
Ps, I even got the movements on video, thought I was losing my mind. The intestines are constantly moving and your uterus pulsates, that is the only explanation I can think of.