If he is turning a jab into a hook, he'll be tipping it off with his feet. Are you reaching out to catch his jab? You should keep your right hand home; catch the jab right in front of your chin, without extending your right hand, and then all you have to do to block the hook is pick it up a bit and roll your body to your left a bit.
That roll gets you inside his hook so you aren't blocking it flush and puts you in position to immediately throw your hook back at him.