Not feeling well after legs and back workout

I am 45 years old, and generally in a decent shape. I am nearly done with the first round of P90x. I'm at the end of week 11. So 2 more weeks to go, and my plan is to start over and keep going. I have always dreaded the legs and back day because it's the most difficult workout to me. I believe, part of the reason is that my legs are already recovering from the yoga x from the day prior. And then you add a bunch of pull ups to the routine and I'm sweating like crazy, and the heart rate is off the roof. As the title states, a couple of days ago, I went hard at legs and back, and followed it up with the ab ripper x immediately after, which I normally do. The next morning, I woke up with full body aches. I could barely move. My stomach also hurt from the inside. I don't even know if it makes sense, but it felt like my intestines had gotten tangled. It was brutal. I felt feverish, but didn't have a running fever. I took a couple of days of rest, I took painkillers alternating between Tylenol and Advil. And I slept a lot. And I mean, a lot. Nearly 15 hours. Today, I feel a little better. The body aches are gone, but I've had a diarrhea all day. I'm sorry about the gruesome details. But I've had to go to the bathroom at least a dozen times today. I feel a little weakness, but otherwise I feel fine. I'm thinking about taking another couple of days off from P90x and maybe just go out for a light jog instead. I guess I just wanted to share my experience with the community, and I am wondering if anyone out there has had a similar experience. I don't know what happened. Maybe I was coming down with something, and the intense workout made it worse. Maybe I was dehydrated and my body got overheated. I really have no clue.

Update Feb 6, 2025: today is day 3 since my legs and back workout, and I feel like I am back to normal. The body aches are gone, and so is the weakness. I'll continue the program, but I have decided to keep reminding myself to take breaks and pace myself. Listen to my body, and keep my heart rate in check.