Atti's routine or lack thereof

Atticus is currently only ever awake for 45 mins at a time and then sleeps for 45 mins and the cycle continues from about 7am until about 7pm. He then sleeps from approx 7.00pm till 4am and then 4.15am till 7.00am so there's absolutely no problem at all at night time!According to all the books and my maternal health care nurse he should be awake and sleeping in at least one and a half hour lots at his age but I don't know what to do to extend the times? I put him to sleep when he shows tired signs. I'm watching the baby, not the clock. I've tried to extend his catnaps by resettling him too but he gets really upset. I don't know whether I should be trying to fix his routine or just accepting that this is how he is?