Just Today I Have Been Experiencing Fluttering Or Like Rolling

Just today I have been experiencing fluttering or like rolling feelings in my abdomen. It does not hurt but has been pretty continuous for about a half hour now. I know whay gas feels like and it does'nt feel like gas, no pain. My last period was April 22nd to about April 26th. My periods are sometimes irregular, but I also took a pregnancy test maybe four or five days ago which came back negative. It was not a first morning urine like as soon as I woke up but soo after and I peed a lot in a cup and then dipped the test. I am just wondering what it could be. I have also been urinating frequently and have some back pain from lower to middle areas, but sometimes goes up to the top of my back. I am thinking about making a doctors app. but this fluttering does'nt hurt and has been pretty much continuousfor the last half hour. Can you help me on this question?