When people (and babies) are overtired, our bodies secrete stimulating chemicals that keep us awake. It is very likely he is just so tired he can't sleep during the day (when there is light and a lot of other external stimulation to distract him from sleep). Most babies need 14-16 hours of sleep per day when they are that little. He is too little to be able to soothe himself to sleep, so crying it out won't work. It's just going to take you some time to figure out how you can help him get to sleep during the day.
There is a great book to check out from your local library: "Healthy Sleep Habits, Happy Child" by Dr. Marc Weissbluth. It will explain many of the signs to look for and how to soothe babies to sleep. It will also explain how much sleep babies need at different ages, and how you can help them get the sleep they need.
At 9 weeks, he should still be going to sleep after being awake for at most 2-3 hours. The more tired he is, the harder it will be to put him to sleep. Try putting him to sleep for a morning nap around 7am if he is waking up at 6. He is probably so overtired that he can't get himself to sleep if he is awake longer than that. When babies are well-rested (as they typically are after a good night's sleep), they will have an easier time getting down for a nap. This is why trying to get him to take a morning nap after being awake for only an hour will probably help him take more naps throughout the day. Once you get his morning nap in order, try putting him down for his remaining naps after he has been awake for an hour or two. It takes a few days to see results, but once he is better rested, you will be amazed by how much more he sleeps.
It seems counterintuitive that the more tired they are, the harder it is to get them to sleep, but if you try to get them to sleep before they get really tired, they have a much easier time getting to sleep (and staying asleep!). The more sleep they get, the more they will sleep.
Healthy Sleep Habits, Happy Child by Dr. Marc Weissbluth