Showing?

I will be 9 weeks on Thursday and I have had two miscarriages. I have never got this far along, and I have been to my Doctor and seen my baby twice ultrasound, the Doctor says each time the baby is looking good and growing right. January 21st, he said I will be getting to hear the baby's heartbeat (still worried, bc my history), another worry is that it is my first pregnancy and I am a very slender girl,, I see all the post with baby bumps and I am still not showing. Should I be worried?