Ok. First of all, it is very difficult to get accepted into a PhD program in clinical psychology. The acceptace rate is ~8%. Many say it is more difficult to get into a PhD program in Clinical Psych than Medical School
Applicants are generally top notch, have GPA 3.8 or better, and GREs greater than 1200.

You do not have to a MS, but would need the prereqs for the particular psychology program.

It is a plus that you are good with numbers, because research requires the application of statisics and study design methods to the pyschological problems.
Most PhD programs pay their students to goto school, with a stipend, tuition, and health insurance.