Is this A False Pregnancy. ?

I have been to the doctor there times to see if I was pregnant. She told me no but my uterus is growing and I have all the symptoms. I have been spotting every month since I had sex. No cramps , no clots. Just spotting . Not a real period . I have been confused but not really scared or wanting to be pregnant . I haven't had any children. They say usually you have a false pregnancy when you are in thm criterias. This is my third month. I always press down on my uterus to see what it feels like and it feels hard right in the middle of my abdomen. I feel the fluttering movements but I always just say that it's probably gas. 18 and really confused. Im thinking about calling my doctor to have an ultra sound done but half the time she Keeps telling me that im not and won't confirm it with a blood test. She just goes by my urine test but I always took them test in the afternoon and had consumed a lot of drinks. That can dilute the test so I don't count them to be accurate . What do you think could I be pregnant or false pregnancy.