Sending healing hugs, Grammy! I suffered with a recurrent Cdiff infection some years ago. At the time, I didn't try any herbal remedies because my gastro suggested a FMT and I agreed to go that route. Thankfully, it cleared things up.
I see that you've already tried oil of oregano. What about
manuka honey? I use Wedderspoon monofloral 16+ when my fistula gets fussy and it usually helps the infection to drain. Here's an older study on manuka's effectiveness against Cdiff: https://pubmed.ncbi.nlm.nih.gov/23651562/