hows your baby now....?
I never faced such situation so can not recommend and suggest anything
but I will say and advise you to consult another vet, in fact 2-3 vet if you ae so insisted on using Ivermectin
because if your vet has stopped you using this, then he/she must have some reason and of course knows better than you... but still his words are not the last and that's why consult some other vet...
and at least make sue that there is no side effect of Ivermectin, before using it, because on wrong step can cause you feel sorry for life time
Best of Luck