Missed miscarriage

I think I'm experiencing a missed miscarriage. I conceived in June and didn't have an ultrasound until 12 weeks (yesterday) but the baby only measured 6weeks 6 days and my hcg levels are at 3241. Has anybody gone through this I'm not getting many answers from the doctors I've seen so far. I'm wondering what happens next and how long I'll have to wait before we try and conceive again.