How do I get my 8 month old to sleep longer?

He used to wake up at 7:30am and it was perfect. His nap time is 10am and he wasn't fussy, mornings were a breeze. I have no idea what happened but he has started waking up at 5:30-6am and refuses to go back to sleep. I have even brought him to bed with me out of desperation to get him to sleep but it doesn't work anymore either. Mornings are hell now. He won't play like he usually does, he usually loves books and won't have anything do do with them in morning. He used to eat a good breakfast and now refuses. If I don't keep him up until his 10am nap time then it shifts everything else in the day and makes night hell too. I've tried pushing back bed time, I've tried rocking for hours, I've tried nursing, I've even tried letting him cry. I'm at a loss how do I get him back on schedule of waking up at 7:30? Its been 2 weeks of this so far and I'm a my wits end.