Looping audio distorts after a few loops

I have a soundbyte that I'm trying to loop over a longer period of time. I set it to loop and extended it, but after the first few times the peaks get more extreme and the valleys get more extreme. If I go halfway through the loop and click play, it starts out fine and then starts to distort. Basically it's just in the preview in-program. After exporting it, however, the distortion exports too. I can physically see it in the wavform. I'm a little confused.