No, campen in the beginning will not affect oxidation, that happens
after fermentation.

You need to use campen each time you rack, at least 1/2 tablet per
gallon. You need to keep the container full and under seal too, either
an airlock half full of water or a cap of some sort if you are sure
it's done fermenting.

Check your arilock seams, sometimes the mold making seams leave a ridge
that needs scrapped off. have seen that cause oxidation because the
wine is not sealed off.

Joe