First Time Mom

I'm a first time mom, and paranoid about losing the baby. I feel pregnant some days (sore boobs, mild nausea, etc...) and other times I have zero symptoms. I haven't thrown up yet. I have pretty constant cramping, but no blood. My doctor doesn't do an ultra sound until 12 weeks, which is stressing me out because I want to know that things are okay. I'm approximently 7 weeks (going by last period). Suggestions? Is it normal to feel this way? Is there anywhere else to go to get an earlier ultra sound? How do I know the baby is okay?