There is a tact and an art in this. You need to talk to your husband in a manner that he understands your point.
Instead of confronting you can explain that you would like to take care of things but for this to happen there is a need to allow you the needed freedom. It should not come across as anger towards his mother but as part of care. You can tell him that you understand his mother’s love which is natural and do not wish to come in the way of her love.
All that you need is that now that you have come that you would naturally like to be fully involved in his care, especially in things like organising your room. I am sure with patience and goodwill there will be harmony and happiness rather than anger and frustration.
Affectionately,
Alok da.
