Enlarged uterus but negative pregnancy test

Hi my name is Allie and I have a question for you. About three months back I went to my doctor because I was having pregnancy symptoms. He gave me a urine test and it came back negative. I told him that I have had feeling of movement in my stomache and that I knew what it felt like to be pregnant because I have three boys. At that time I was starting to have fluttering kicking feelings and a month before that I told my doctor I was have a quickening feeling like you would at 4 months. Now I have strong kicking and movement with an even larger belly but keep telling myself its gas. My doctor gave me a pap and asked me a very odd question. He wanted to know if I ever had surgery or anything ever done on my cervix; I have never had anything done to my cervix and then he checked my overies during the pap and then when he checked my uterus he said it was enlarged and wants me to have an ultrasound. My monthly cycles still come but are very irregular now for the past 6 months. Any ideas?