DS (6 months) has had a cold for the past few days. He's been quite tired during the day and waking a million times during the night because he's bunged up or coughing. Last night was the first night where he only woke up once to be fed, hallelujah. Today however he seems even more tired. I put him down to sleep at around 11.30 and he's still asleep now almost 4 hours later. Normally he only naps for around half an hour. Should I be worried? Because I am.