my beautiful happy sleeper GONE! now its a nightmare

well where do i start! ds who is almost 12 months used to be a fantastic sleeper, never heard a peep out of him through out the night and used to wake in the morning with a big smile on his face and happy to see us.

Now, he wakes during the night, screaming his head off, then i go in there and he won't settle unless i pick him up. After a cuddle, i put him back but, as soon as I put him over the rail to his cot (yes before i even put him on the actual mattress) he starts screaming again, so i eventually take him into my bed and he falls asleep instantly (only if I am cudling him though). When he wakes in his cot in the morning (if he has slept thru in his cot) he is not happy anymore like he used to be.

what is happening? why won't he self settle at night anymore? he used to do it, what has changed? why isn't he happy to see us in the mornings anymore? why does he cry to let us know he is awake, instead of chattering and playing in his cot like he used to?

don't get me wrong, i love cuddling him to sleep, but then i can't sleep for fear of him falling out of our bed or something.

is it because he is teething? (he only has one front tooth, which isn't even all the way thru yet and the others are coming too). is he going through a growth spurt? did i do something wrong? is it the food he gets (he usually gets what we eat for dinner, which is vegies and a little bit of meat).

can someone please shed some light on this for me? i don't know anything as this is my first child. I don't want him getting into the habbit of needing to sleep in our bed, I would love to co sleep, but I just can't sleep that way, so its not an option for us.

what should i do? I don't want to let him cry, i hate that, but i don't want him getting into bad habits either if that makes sense.

anyway thanks for listening and hope someone can help.

We just had a week of this that seemed to coincide with a bit of a cold - back to much more normal now.
For the cuddling - think about biting the bullet and arranging your bed so he can't fall out (or can't hurt himself) - put the mattress on the floor if you have to for a while. Then you can at least get some sleep yourself (which is probably the most important thing).

This is also a stage where separation becomes a big issue for some kids.