Welcome to healthcare magic!
Safety is not known for infants and should be stopped if you want to give the child any other medicines like an antibiotic.
It is very marginally effective in increasing the milk secretions.
I think you can taper this over a week and you will do well without domstal
The Soya formula is as good or better than the cow milk but baby should receive absolute breast feed till he is 6months.
I hope this advise would be helpful for you.
Wish you a great health!