Antibiotics and possibly many other medications your mother may have used before or during pregnancy and all of the Antibiotics and possibly many other medications you used during your lifetime.
Crohns is caused by medications.
Research the FMT and forget about the Amalgams.
Amalgams are bad, but Amalgams are just a drop in the sea.
Research also IBD diets.
What you need is possibly 20 - 100 different microorganisms, microorganisms you are missing.