This is Class Tracking, not user names: "Yes, we are wanting the transaction total for each user."
User names is how you control Access and limited rights, such as, some people have a log in that does not allow them to Print Checks. It's not a Financial option; it is a Usage and Audit Control provision.
"We had previously used software for a veterinary clinic and that is type of reports that we had printed off for each of our doctors that showed totals."
Yes, that is Class Tracking.
"The report that I customized is exactly what we want except for the fact that all users (doctors) are on the same report instead of having a report for each separately."
Because "user" is not financial, but a Clerical Control, aspect.
You want to Enable Class in the accounting preferences. You want to set up three classes: one for each of the two doctors, and one "Admin" class, typically.
Class = Divisional or Departmental reporting of allocated amounts.
Please see my attachment.