I'm on my fourth cycle using lady comp, and it's been good so far except that at this point, I've gotten a red light every morning for almost three weeks now. I've been taken my temps the way I should, and no pills, what's going on?

You're simply ovulating later than usual
If you are plotting your temperatures on a chart, I'd be glad to take a look to help you assess the situation.
If you're not familiar with charting, www.fertilityfriend.com is a great place to start.

but it showed the blinking red light 8 days ago, which means it's saying I ovulated then, so why am I still red?

No, in the current cycle, the blinking red light only stands for the predicted ovulation date!

As you go along, LC will become more accurate in predicting your O date, as well as narrowing your fertile window to the minimum.
But in any cycle, at anytime, your body can have a delayed for many reasons, illness, travel, high stress, etc.

Only once the cycle is closed, on day 5 of the new cycle, you will see the red light reappering and often in a different place, and that's the confirmed recalculated ovulation date (which can still be not realistic, because it does its particular math)