pls help

I went to my doctor awhile ago. I don't have any symptoms of miscarriage or spotting or something. All my bloodtest and urinalysis are normal. Then my doctor asked me to lyedown to check the heartbeat of my baby using doppler. she didn't hear anything. I am 13 weeks and 2 days pregnant by the way. I am really worried coz of the heartbeat thing. Is this possible? she told me that maybe because my uterus is in tilt position i dont know. pls enlighten me. Will have my ultrasound tom. huhuhu