Position doesn't matter for a long time. My mom said I was in a breech position at her last appointment before I was born, but I flipped over at the last minute. But at this point, they are still tumbling and moving around a lot.
At my appointment Wednesday, my doc was able to push on my belly and tell me what position baby boy was in by feel. I was impressed that she could feel head and butt through all my fat layers. But I'm pretty sure he's still flipping around, because some days I feel big kicks on my cervix, and other days it is higher on my belly. Those higher ones I'm feeling through the anterior placenta! So they may not have to do another ultrasound to see where the baby is. If your baby is kicking upward at the end, I suspect you'll know it. 