Should I go back to school or get a new job?

I work in the mental health field and have a Psychology degree but I want to get out of the field. I am really unhappy with my work and I have to have a couple part time jobs to supplement my income. I only make $20k a year ...pathetic I know. I was in a Surgical Technology program but decided it wasn't what I wanted to do when I only had a couple months left to go. Needless to say I'm feeling a little lost right now and I am trying to pick up my self-esteem off the floor so I can get moving in a direction. I would like to get my biology degree so that I could study botany, forestry, wildlife biology or possibly go to medical school for pathology. My question is ....should I just go back to school or find some full time work that could provide me with more income so that I can save money and pay off debts before going back to school. I guess I'm trying to find the next best step but I am coming up short.