@MindOverMatter It's very competitive, but not as competitive as PhD programs. Hot Metal Bridge had maybe 150 applicants for 5 psychology slots? Compared to 200-300 applicants for clinical programs on average.
I have an undergraduate degree in psychology, so I did not make the transition you are making. But many people make the transition. My boss (I work in research) has a BS in Economics and is now a clinical psychologist. It's absolutely possible. To make this transition possible, you need to 1000% be involved in psychology research. This is how you'll get the letters of recommendation you need, and prove to PhD programs you are serious. While taking courses can help, there's almost nothing as valuable is volunteering (as much as you can) time doing research with faculty in a psych dept (e.g. 10 hours/week doing volunteered psych research).
PhD programs value research experience almost more than GPA, GRE scores and university prestige. I say almost because those things are damn important, but what separates good applicants from great ones is what kind of research experience they have, how much they have, and if they can produce publications and presentations from said research. PhD mentors look to to see if your research experience "fits" well with theirs, and if it does, you'll be offered interviews.