Nothing visible

So I went to my first appointment today and my dr did a transvag ultrasound and all that was visible was a gestational sac measuring 5 weeks 4 days. My lmp is 2/1/17 so I should be 7 weeks today. I got a bfp 3/12/17 and at the office today too. So she sent me to do hcg and progesterone levels today repeating it 4 times and ultrasound again in a week. Our first was a stillborn at 5 months and then our Rainbow Princess, who is now 10 months old, and this baby #3 I don't know what to think. Is it just not as far along as I thought?! So nervous!! Anyone else go through this and still continue pregnancy? Also I was told to stop breastfeeding because it causes uterus to contract and can cause miscarriage....