A post bacc doesn’t need to be formal program. You can always take additional undergrad classes as a non-degree seeking student. However, non-degree seeking students are not eligible for federal financial aid and at most colleges non-degree seekers are given lower enrollment priority than full time students.
There are 2 kinds of post bacc, @frazi78 —Career changer post baccs for students who have not taken their pre-reqs and ** academic grade enhancement ** post baccs for people who have completed their pre-reqs, but whose GPAs are too low for medical school.
You need a academic record enhancer.