An ejaculation contains several different fluids. One, seminal fluid is the whitish/creamy colored one that only helps in the ejaculation process. The other, is actual sperm. Usually yellowish in color and often clumpy or jelly-like. I'd suspect that is what you are describing as chunky. You'll notice it more depending on the amount of sperm available in an ejaculation. This is determined by the frequency of ejaculations, the more you have, the less you'll notice the concentration. Nothing to worry about at all!