Sadly unless one works for government/state agency/entity and is unionized, employers could pay whatever salaries they want (as long as it meets minimum wage requirement). There sometimes is no rhyme or reason to what people get paid. They could hire ten people in retail for example and offer all ten different salary and there is nothing you can do. They can give different raises, and it’s not always because of who does a better job. Also if you are a part time employee sadly your hours are not guaranteed. They can cut them any time

You don’t even supposed to know what other people get paid. Is it fair? No. But that’s how it works.

I think it’s worth to take a look if other doctors offices hire. You have enough experience and you deserve better treatment