Bisping fought just eight weeks ago, when he scored a third-round TKO over Jason Miller.
"My body is feeling pretty beat up right now to be honest," Bisping told ESPNChicago.com. "I've been training almost nonstop since September. After my last fight, I took two weeks off and then hit it again really hard."
UFC president Dana White thought because Bisping came out of the Miller fight unscathed, that he would benefit from fighting Demian Maia on Saturday in the United Center. And then when Mark Munoz dropped out of his bout against Sonnen because of an elbow injury, Bisping was elevated to a fight that could lead to a title shot for the winner.
Bisping said he's ready, but the short recovery time has made an impact.
"I'm not burned out," Bisping said. "I'm almost there.
"I'm mentally burned out, I'll tell you that. I'm sick of it. I need a good break, but at the same time I'm so excited for this fight. This is going to be a great fight."
Sonnen is known for his extensive wrestling background and for putting opponents on their backs. Bisping said he is ready for the challenge.
"I'm not going to let him take me down," Bisping said. "I've never been held down ever in my UFC career, and I don't think he's going to be the first one to do it. I think I'm going to have to overcome adversity in the fight. I'm probably going to come out with a couple bruises black and blue, but ultimately my hand is going to get raised, and I'm going to win.
"I relish the change in opponents. In some ways, they are very similar being grapplers and southpaws. Chael has a much bigger advantage in wrestling. He has a bigger name right now and the momentum behind him. I'm excited to fight him. I think it's a good matchup for me. I'm confident I'm going to get the win."
There has never been an English champion in the UFC. If Bisping wins, he could be given a title shot against reigning middleweight king Anderson Silva.
"Pressure is always an element," Bisping said. "I'm excited. I want to do this. I'm doing this because I just chose this career. I love to do this. I'm deliriously happy. Saturday night, I beat Chael Sonnen, I fight for the world title; that's even better."