Abnormal Pregnancy?

I found out I was pregnant about a month and a half ago and I'm currently 12 weeks pregnant....I've been having a hard time because my doctors claim they can't see a baby in my uterus with an ultrasound I've been really scared lately because no one has been able to give me a for sure answer about how my pregnancy is going.....I haven't had morning sickness at all but I have had tender breasts and cramps (mild) I also have a bicornate uterus I want to know if anyone has gone through anything similar