DS was like this. I couldn't leave a room without hysterics. Couldn't shower alone, go to the loo, even cook dinner without DS in my arms (DH was a fat lot of good at this point).

It's worth looking at it from the "what he's thinking?" viewpoint.

DS was thinking: I don't like it when Mammy leaves. She is my rock, my anchor, my world. I can cope for three minutes if Night Garden is distracting me so I don't know, but no-one else is good enough. But I need her.

Now DS thinks: Mammy isn't here. She is still my world. But I know she will always love me and be there for me, I see her every day and right now she's not here but my mate Charlie Brown is so I can play with him until she returns.

In the middle of the night, when he's inconsolable, I can calm him by singing "I promise I will never leave you And we will always be Forever you and me You'll always be a part of me" (Lullaby (Goodnight my angel) by Billy Joel). He needs to know I'm there for him, even when I'm not.

It sounds like your DS2 knows this. He is independant and happy to not have you there for short times. But a week/five days is a long time to not see your world. He will recover once he realises that you are there and always will be.

Yes, it's hard for a baby when the mother needs to be away for a long time (as you did). But he will recover well, in time, so long as you let him know you always love him, no matter how clingy he is. Which is hard. But I know you can do it and you will do it: even when you snap (you may not but I do!), you can still apologise and let your DS2 know you still love him and will always be there.