Financial aid for medical bills insurance won't cover or only cover part of?

I finally found a medical practice to address my complex health problems but my insurance (Anthem BlueCross Basic Hospital PPO) won’t cover any of my bills. And because it’s a private practice it’s quite expensive and they don’t have financial aid like some hospitals do. I also found out that I need surgery for endometriosis but the surgical center where my surgery will take place does not offer financial aid & my insurance will only cover part, leaving me to pay upwards of $10–15,000. That may not seem like a lot of money to some but it’s huge to me. I have a steady full-time job but I work for a nonprofit so my income is pretty minimal. I’ve applied but don’t meet the criteria for MediCal.

I’m hoping that someone knows other ways, organizations, etc. to get financial aid so that I can have the surgery. Trust me, if the surgery was at all “optional” I most deff wouldn’t have it.

Thanks very much!!