Thanks for the query to H.C.M. Forum.
In all you took roughly 50 ml milk of magnesia
This is very high dose .This produced diarrhea
and hyper acidity ( so was nausea
In my opinion this is very natural .
Use plenty of lukewarm water sip by sip .
But if nausea is severe you may need proton pump
Banana and curd will also help.
Still diarrhea you may need some anti diarrheal drugs after consultation with a doctor.