Sweet dreams have disappeared.

We were spoiled with Wyatt's earlier sleep habits, 9:30-6 or 7 straight. We're now faced with a baby that can be up till 10:30 or 11 and wakes at least once a night for some food or just because he's unhappy. *sigh* How did this reversal happen? More importantly, how do we halt the change and make it do a 180??