Yellow Clumps

Can anyone help me answer this question? I've noticed little yellow clumps of stuff in my semen lately. Sometimes there's a lot of it, and sometimes there's just a little of it. They're like a darkish yellow color, and about the thickness of chilled Jello. Sometimes they're quite large clumps, and other times real small. Does anyone else have this problem? Would greatly appreciate any info you could give me as to what this is, and the cause. Thanks.