Where's my happy baby gone? 3mo given up sleeping.

[UsedToBeAPixie]

New on here, so forgive me if there's a thread on this already...
My LO is 12 weeks old and before this week was going down to sleep at 7.30pm, self settling and sleeping til a feed at 2.30am, then on again til 5ish. He did this from around 7/8 weeks and was like clockwork. What he didn't do was sleep during the day - he just snatched bits and bobs after feeding - so I had to take him for a really long walk midday to make sure he got a bit of shut eye.
We've been trying to implement naps a bit more during the day as he's starting to turn into a goblin earlier and earlier in the evening and I can see he's really tired, but he's not keen. I think we'll get there though, eventually (I bought the no-cry nap solution book after seeing it recommended on here so I'm hoping this will help).

My problem is that the last 2-3 days, he's started waking up every hour at night - sometimes stretching out to 2hrs, but sometimes only doing 30-45 mins. He cries and cries, so most times I just feed him even though I suspect he's not hungry. He's so tired during the day that if I manage to get him down for a nap, he's really really unhappy when he wakes up.

He was such a happy baby, playing with me all day before that it just makes me sad that he's not happy any more unless it's first thing in the morning.

Could this be teething maybe? It sounds like this 4mth sleep regression thing that I've read about on here but it seems a bit early.

[OwedToAutumn]

It could be either of those things.

You probably just need to ride it out, unfortunately, doing what you're doing.

But whatever you do, don't listen to those people who say he is hungry, and to put some baby rice or rusk in a bottle for him!

[UsedToBeAPixie]

Thanks, I hope it passes soon - poor little lamb, I just feel really sorry for him :(