Alex Trebek is undergoing another round of chemotherapy for his stage 4 pancreatic cancer.

Trebek revealed the tough news on GMA saying that his doctors noticed he lost a large amount of weight and saw his numbers "skyrocket" after finishing his first round of treatment.

I was doing so well. And my numbers went down to the equivalent of a normal human being who does not have pancreatic cancer. So we were all very optimistic. And they said, 'Good, we're gonna stop chemo, we'll start you on immunotherapy.' I lost about 12 pounds in a week. And my numbers went sky high, much higher than they were when I was first diagnosed. So, the doctors have decided that I have to undergo chemo again and that's what I'm doing.

Trebek described cancer as "mysterious in more ways than one" saying that "excruciating pain" and "fatigue" were just a few of the tolls that it has taken on his body. He also spoke on his experience with the "surge of sadness" and "depression" that comes with a diagnosis this serious.

When it happened early on I was down on myself. I didn’t realize how fallible each of us is in his or her own way … I talk to the audience sometimes and I get teary eyed for no reason. I don’t even bother to explain it anymore, I just experience it. I know it's a part of who I am and I just keep going.

Trebek announced the initial diagnosis back in March but remained optimistic. He finished his first round of chemo and filmed the 35th season of "Jeopardy!" The legendary host says support has been overwhelming, with fans sending him everything from blessed items to "holy water from places of worship around the world."

With all of the fear and uncertainty that comes with cancer like this, Trebek reveals that the idea of passing "doesn't frighten him."

I realize that there is an end in sight for me, just as there is for everyone else. One line that I have used with our staff in recent weeks and months is that when I do pass on, one thing they will not say at my funeral is, 'Oh, he was taken from us too soon.' Hey guys. I’m 79-years-old. I’ve had one hell of a good life. And I’ve enjoyed it … the thought of passing on doesn't frighten me, it doesn't. Other things do, the affect it will have on my loved ones ... it makes me sad. But the thought of myself moving on, hey folks, it comes with the territory.

As far as what makes him happy?

As long as I can walk out and greet the audience and the contestants and run the game I'm happy

Best wishes, Alex. Sending all the good vibes your way. You got this.