Prego sign and confusing docs appointment?

Hi well i have been having many signs of pregnancy now for about 6 weeks constantly need the toilet smelling everything sickness most signs along with 3 poss test and 1 neg. My stomach is incredibly swollen and hard has been like that for 5 weeks went to docs first week just said to leave it. it will go down on its now went back this week as its the 5th weeks its been like this and has got really uncomfortable as its grown. Doc felt my stomach and listened to it did another preg test said if its neg am still sending u 4 an ultrasound it was and she has requested for an appointment for me was just wondering why she would have done this thanks any info please. xx