In the third quarter of a football game a month ago, Buffalo Bills running back Karlos Williams was tackled for a seven-yard loss. You probably don't remember the play, but it not only cost him almost a month of his first NFL season, but also the ability to do basic human activities for the next several weeks.

"I thought it was just my stomach acting up, throwing up," Williams told reporters Monday. "Me just feeling a little nauseated. Headaches, pains toward the end of the game. I thought it was just me being tired, me being dehydrated.

"But definitely as I got home, I knew that something wasn't right. My balance was off. It wasn't dehydration. I was drinking Pedialyte and water at halftime, so it couldn't have been that," Williams continued.

Williams returned to the Bills' training facility a few hours after leaving, and was immediately placed into the NFL's concussion protocol. His fiancée had to drive him, and she would help take care of him for almost a month.

"Having really bad headaches. Not being able to sleep. Not being able to eat. Kind of side effects I've had over the years from having concussions: just being very, very groggy," said Williams when describing the symptoms of his third concussion. "Wanting to be up. Wanting to watch things. [But your] eyes hurt real, real bad. Very sensitive to light. Things like that. You're always tired. You can't sleep. Your head's always kind of pounding, throbbing. Your head feels tight."

Williams continued to reference the headaches the entire time he was speaking with reporters. He and his fiancée darkened their home - no sunlight, no artificial lights, no television, no driving for more than a week. After a period of time, he was able to slowly reintroduce everything. He had a setback when he tried lifting weights.

Williams thanked his fiancée repeatedly in the interview, but he's not worried about the long-term effects of his concussions, and says it won't alter his running style.

"[I'm] ready to play football," he said. "It's not going to change the way I run the football. It hasn't changed the way I run the football. I run the football with attitude, and I think that's what the coaches expect from me coming back."