Help please-2 year old won't go to bed!

[Bubbaloo]

Ds2 will be 3 in April and has always been a great sleeper,sleeping 12 hours+ every night.
He is still in a cot and about a month ago,started screaming after dh had read his bedtime stories and tried to leave the room.The screaming was hysterical so we thought that maybe he'd be better in a bed now and perhaps he no longer wanted his cot.
He loved the new bed but wouldn't fall asleep on his own-dh laid with him for 20 mins or so,til he fell asleep.He was then wide awake and screaming again around 1am,refusing to sleep anywhere except our bed.After a week of this,we thought that maybe he's not ready for a bed yet,so he's back in the cot.Tonight has been a nightmare.He's refusing to sleep in his cot again and is currently asleep in our bed and again,dh had to lay with him til he fell asleep.
Really have no idea why he's suddenly got a problem with going to bed and also don't know whether to keep the cot in his room,or put the bed back in there.
Although he's nearly 3,he is a very young 3 year old and doesn't talk,so he can't even tell me what the problem is.
If anyone has any advice or answers,that would be great,thanks

oh dear - poor you. Can he speak at all? Can you understand if he might be frightened or ill or just messing about?

I'm inclined to think it may be something like an ear infection or something maybe?

Has anything changed recently? Could he be feeling anxious or stressed?

Occasionally our just 3 year old gets in to a tizz about something and is in effect to scared to sleep on her own. We pull her in to bed for the night and then she's fine the next night to go back in to her bed.

It;'s always very difficult when they can't communicate with you?

Do you know why he isn't talking if you don't mind me asking?

Thanks.
No,we don't know why he's speech delayed but he does get very frustrated.
He says about 20 words,understands us,and we mostly understand him.
I did think that maybe he was starting to get afraid of the dark,so we bought one of those night light torch's,but after a day,the novelty has worn off and he's not interested in it.He also loves Peppa Pig,so we bought him a George pig duvet set and rug,and as much as he loves it,it still hasn't worked.
Everyone keeps telling us not to let him in our bed,but easier said than done,when he won't sleep anywhere else