Egg Retrieval

I am doing IVF for the first time this cycle. I had my egg retrieval done today & was really disappointed. My sonograms showed that I had 10 follicles that were all what my doctor said were a good size (15+). When they did the revival today I only ended up with 5 eggs. Half of the follicles were empty. Has anybody else experienced this? I am worried now that I am not wind up with any eggs to transfer.