First ob appointment, worried


I had my first appointment yesterday with an u/s & by LMP I should be a little more than 7 weeks. Dr said I was measuring 5w6d. I'd been tracking bbt, cm, etc, so I don't think I ovulated late. This is my 3rd pregnancy, but first after the age of 35. The doctor said it's a waiting game. I have another u/s in two weeks, but I'm not sure how I'm going to wait that long. I have a second blood test to check hcg levels tomorrow. Has anyone had a baby measure behind & end up perfectly healthy or anyone miscarry? I don't know what to expect or how to think.