I have a couple of comments about this, having experienced similar problems with my two boys (now 3 and 6).
First, you mentioned you have no schedule, which in our experience is crucial to a good sleeping pattern. A schedule needs to be reinforced by a routine. You drill it in every night and stick to it as best you can. Our schedule looks something like this:
—Active time after dinner for wearing them out as much as possible. This ‘wrassling time’ usually involves me rolling around on the floor with them while they kick me in the nuts. When it’s summer, I try to take them out for a walk or something.
—Head up for bed, brush teeth, pee, etc
—Read two books, tell two stories.
—Lights out
Always do this at the same time every night, try not to stray from the schedule. Talk about it before hand, give them warnings about what is coming up: “Boys, in 10 minutes we are going up for bed. Do you want to wrestle before then?”.
Kids need structure, and when they don’t have it, it becomes obvious quickly.
Another thought is that perhaps there is a root cause you could be looking at. Why might he stay up all night? Is it dietary? Have you tried cutting out sugars and caffeine? I’ve noticed that about 2 ounces of Diet Coke after 5pm is enough to keep my 6 year old up until midnight.
Anyway, sorry for the rambling…I feel your pain.