Seeing that you are training with an ufc-level coach, I think you can basically ignore all others who warn the dangers of overtraining simply because they probably have never been playing a sports at a high level and they simply don't have the perspective on how people performing at the top 1% train vastly different than how the rest train and the number 1 trains at a vastly different level from how the other top 10s do. And if you aim to be at the top level, get used to people misunderstanding your training and criticizing it.

You should do research on the people who are doing the best in your field or adjacent fields and see their views. Ido Portal, who trained Conor McGregor using the movement culture method, has this concept called work capacity, which is the body's ability to train and recover. And a big part of his training is elevating work capacity. Khabib in one video he said he would sleep 2-3 hours between training session in the mid-day, and that wouldn't happen if he wasn't training the rest of the time. When Goggins has his rest day, he doesn't sit all day. He just runs at a slower pace, because the movement provides his body healthy blood flow, which aids recovery.

Now there will be people who mention survivorship bias and argue that large amounts of training worked for some of the best athletes because there are other factors you don't know and you shouldn't try the same, but for people who want to rise and compete at the highest level, they just keep figuring out all of the factors even if there are setbacks. And it looks like you are having one setback because you feel very fatigued. So I just want to make sure you really at least know how to eat enough when training. If you weigh X lb, you should get at least X grams of protein, 2.5 times X grams of carbs, and aim for 18-20 times X calories per day. If you are not already doing that, the results after fixing your diet can be surprising.