You don't want to take magnesium if you have parasites. parasites can create a bio film that protects them from our immune system. The bio film is made of calcium, magnesium and iron.
So stop feeding the parasites with the magnesium. Try breaking down the bio film with 2 capsules of bromelain twice a day between meals. This is a digestive enzyme that will break down proteins. Between meals so you break down the bio film and parasites and not food. This was a game changer for me. My Naturopath suggested it.
You could also try adding betaine hydrochloride to your meals. This will increase your stomach acid, making digestion better and it MAY help destroy the parasites. My belief ( and it is only that) is that the parasites can deactivate either the production of stomach acid or have developed means of surviving it. So adding to it may help overpower them. We also tend to lose our stomach acid as we age.
BTW, I would suggest that you eliminate all other supplements/vitamins except for stomach acid (betaine hydrochloride), zinc and diatomaceous earth. The parasites are benefiting from the supplements/vitamins. Add them back in when you have won the war with the parasites.