I know how you feel. I had the same problem with my now 5 month old. And we are still having a little trouble with the afternoon naps.
But, this is working for me in the mornings- about 2 hours after he would wake up, I would give him a bottle and feed him like I do for his nighttime routine, in his room/dark/soft water CD, rock for a little bit, and then lay him down. He may fuss, but I had to give him some time for himself. Every so often, I would go back in and 'reset' him, giving him his pacifier and making sure he was comfortable, but NOT picking him up. Soothing him by stroking his head or tummy, usually worked to calm him down.
My Dr. said he needed to get used to the idea that after some awake time, there was 'down' time. He also stated that, if he was waking back up after only 20-30 min, keep tying the 'reset' - try to let him work at staying down for 1 1/2 hrs. The 'reset' will let him know that you are still there for him, but he will also learn that this is the time we take a nap. It took about 2 weeks, and trust me, it wasn't easy. Now - the morning naps are almost to where you can set your watch by it! (afternoon naps are getting better, but that's when I'm usually going to work, and my husband is in charge of the naps - it's an entire different subject!)
I think there is a name for this technique - either Ferber or Sears - I can't remember which one. I read up on so many of them, I can't keep them straight!
I hope this helps!
Hang in there!
L. O