Extreme separation anxiety at 4.5 months, and I have to go back to work help!

[Babyitsyou]

DS is my PFB and he knows it!
He's only just starting to go to DH happily, before now he would scream for him.
He screams for all family members including DSIS who is going to be my childcare when I have to return to work mid January. He screams to the point of been so distressed he is red, hot and has been sick. It can take me up to 40 mins to settle him down.
I have to go back to work, extending mat leave is not an option.
I have been visiting DSIS weekly for 5 weeks and he will go to her if she turns him to look at me, but only for 5 mins or so. I have made him have a comforter and dummy to help him settle.
I think I am partly to blame as I haven't wanted anyone else to take him for a walk or anything, only I have fed him. I resent having to return to work and don't want anyone else to take my time away from him.
DM had him for 15 mins but he just screamed and screamed and I felt awful for both of them. If I try to leave him I'm consumed with guilt and end up turning round and coming back to rescue him.
This is causing me so much distress, please help.

Bumping, there must be someone else with a baby clingon

That is very young for seperation anxiety. Does he settle if you leave the room? He may be unsettled because you are there so he wants you but maybe if you were not there he would settle with others especially if he knows them. Also once a week isnt that much for a fourmonth old to get to know someone could you visit your sis more often? He will be fine when you go back to work, babies are very adaptable but you do need to start trusting that others can settle your baby. He does not need rescuing from his own grandma. I dont mean this in a nasty way as i have been there but you maybe need to work on your anxieties leaving him as he is probably picking up on that

Thanks so much for replying.
He is fine at home if I go into another room and will lie in his cot gurgling while I get dressed etc. He used to cry if I left him with DH but has just about got over that now.
I understand what you are saying but at the moment it's a vicious cycle because others can't seem to settle my baby. DSIS says that that's because he knows I will come to 'rescue' him. She has suggested I start leaving him for 15 mins at first, then gradually upping it but I know he will just end up making himself sick. I just end up crying my eyes out.