What’s wrong with me

Dj

I had my last period October 7 I didn’t get one in November and now December I went to the doctor and my pee test was negative but they refused to do ultrasound because I’m “young” and things happen even after I’ve told her I’ve never missed a period and when I was pregnant with my son I had to get an ultrasound done to prove I was pregnant what else can I do to see if I’m pregnant or not??