Do u know what happens next?

Ok... according to my lmp I should be 9w2d today. Last week I went to the doc to confirm a pregnancy. I have a positive test & prob all the symptoms lol. Anyway.. when I got a sonogram we can only see the sac.. no baby but I'm not worried. I was told to come back in 2weeks (Feb 5th). I know this can be a diff situation but I went through this with my last pregnancy and it just turned out that I ovulated a week late so the progression of the baby was a week off. The difference here is that I'm "further along" then I was before. So... my question is: what happens next if there's still only a sac when I go back next WK? That means the baby stopped growing so how do they get whatever is inside of me out? Or is it something that just naturally happens? Aren't u supposed to bleed/ cramp during a miscarriage?

Update: I went to the doc today and it turns out that im 8wks4days based on the measurements. I have to make an appointment for blood work and then back to the doc in 2wks. I guess I just ovulated late like the last time.