21 weeks at first prenatal visit!?

I scheduled my first doctors visit when I was 12weeks and they gave me today. Which makes me 17weeks pregnant. I was in the wrong part if the hospital and when the front desk person told me I rushed over to where I was suppose to be but they informed me I was too late and they rescheduled me for march 11th.. I'll be 21wks by then. I want to know what all to expect and I really want to know if my baby is healthy and the gender! If they dont tell me then, I'll be about 25 wks when I find out and that's too close to my due date. I'd have no time to prepare. So should I expect an ultra sound? Can i call and schedule one to make sure? And what else happened on the first visit? First child and really nervous.