Long story short, as the title says.  I have a Campaign that I run with my friends and I share all my DnD Content with them, and recently one of my players has set up a One Shot and I shared my content there and I found that suddenly all of my Homebrew magic items and Feats and spells, pretty much any surprise homebrew of anything is now easily seen and available for everyone in this One Shot. Is there a way to turn  my Homebrew stuff to only be in my campaign?

I don't see an option to enable/disable homebrew specifically, so I suspect not.

Well shoot, I really wish that was a feature..

If they do not allow homebrew in their campaign, if the character sheets aren't activated to allow homebrew, they wouldn't be able to see it.

I believe if they are homebrew you created yourself you can remove them from your collection and they will still be in your creation list - but because they're not in your collection they don't get shared. This of course means they won't get shared at all so in your original campaign they won't be selectable either. I'm not sure how viable of a solution that will be for you (or even if it works - I've never tried it myself only heard about it).