Angel - maybe he has just come out the other end of a growth spurt? I know that Gabby had some really sleepy days all of a sudden but would snap out of it soon enough. Even now, if she has a really big sleep and hasn't fed in a while, I wake her up. If she doesn't wake up properly, I take the bottom half of her clothes off and that tends to work.
If you are super worried, go and see your GP about it. Or, even go and weigh him at the health centre to see if he is putting on weight. If he is, then there is probably not much to be worried about.