‘Medizin’ can mean either “medicinal drug” or “the science of medicine”, while ‘Medikament’ only means “medicinal drug”.
‘Medizin’=“medicine”, in the sense of a “medicinal drug”, is usually used as a mass noun in both German and English, while the German ‘Medikament’ is always used as a count noun.
In English one would say "My medicine(s)" or " My medication(s) ". Medicaments is not a typically used word at all (in the U.S., anyway) - more archaic or specialized. You will find it in a dictionary but not used in speech or even most writing (unless someone was using a thesaurus! ) :-)