I have read that the priests were not allowed to have sex before they said mass because their hands would touch “christ”
But I'll bet you can't recall where you read that. I'll also bet it wasn't in any Catholic Encyclical or in the Catechism.
It was traditionally part of the priest's required fast before Mass.
Still the case in the Eastern churches -- that's why the Orthodox ordinarily celebrate the Divine Liturgy only on Sundays.
And, as pointed out above, that's a carryover from Jewish practice. Priests serving their "course" of service in the Jerusalem temple did not live with their wives.
There’s a reason why David insisted his men had not been with women before they were given the show-bread to eat - and they were going hungry!