Why is my cat acting so strange?

My cat has been begging for attention all of the time lately. I have spent hours upon hours playing with him, feeding him, petting him, for the past few days. But he just doesn’t stop. This is not his normal way. Usually, he is quite reserved. Usually he doesn’t like to play for more than five minutes a day, or be petted for more than a couple of hours.
This would not bother me if it wasn’t for the fact that he has been biting me when I am too busy to give him attention. Not even hard enough to leave marks or even feel uncomfortable, but still very strange. He will rub his head against me a couple of times and then chomp he bites down.
What is wrong with him?
How do I fix it?