When good sleepers go baaad, what do you do?

[notso]

DS3 22 months has always needed to go to sleep on his own. He has always slept a lot, 3 hour nap and sleeps all night from 7-7.30-8 when well.
He has suddenly stopped wanting to go in his cot for a nap, he cries, shrieks the minute I put him in then falls asleep in my arms as soon as I pick him up. Even once asleep he will wake and cry the minute I try and put him down, like my other DC did as newborns.
I have to sit on the sofa and slowly slump down until he is lying down then slowly remove myself.
He needs the nap, he is past it by about 4 if I keep him up doesn't eat dinner and doesn't sleep well at night.
He is also hard to settle at night I have to sit near his cot for ages until he sleeps.

Have you tried putting him in his pram and taking a walk at nap time? When mine went through this stage this seemed to work.

The problem with that is DS2 3 is napping in bed at the same time. I could try and put him in the double buggy but he would have to sleep outside.

Thanks for the suggestion

I hope it is just an age thing Miaow.
My two youngest share a room too that's why I have been bringing DS3 down so DS2 isn't disturbed.
I am tempted to try putting him in a bed as at least I could lie next to him although am nervous he is protected from DS2 in his cot.
He hates our bed he screams the minute he is on our stairs - loft room.

It is really hard to know how to settle him as he has settled himself from tiny. Even when he has been ill or teething he has just needed patting and shhing. Getting him out the cot made him worse, until now.