So you have no decent post-bac advisors at your university? Maybe seek them out at other schools around you or close to home. Contact some of the PB programs that you think you'd be interested in and talk with the PD there.
I'd slow it down. Take the required post-bac courses at your school or another good one nearby or close to home. Why go away for this? So, if you are away for college now, couldn't you move back home and take the required courses at a university nearby--not paying rent or other expenses? You could get a PT job in a drug rehab or BH unit as a mental health tech if you have taken enough coursework and are willing to sit through their training program. I did this in college, and it was enlightening and I liked it. And I am a small female and they had some big dudes in there w/ drug rehab or other psychological issues. No one ever hurt me. You mostly had to keep your eyes opened, pay attention and know what to look for, and then listen to them discuss their issues or work on Steps or whatever the program required. You'd go with them to group therapy meetings, and this was always interesting to me, b/c in group, people don't allow the other addicts there to BS around the questions. Talk about a reality show. I never heard BS called more in my life. LOL Never got hurt. . .not saying it isn't possible, but mostly it's people that have to get a grip on their problems and you observe them, listen to them, try to keep people safe. I would have worked there after completing my RN, but I was fixated on critical care. Seriously, you just have to be careful and smart about people; but it's not like you kill yourself on this kind of job--at least not at the place I was. In nursing school, I was in a huge and scary psychiatric hospital with many locked units. Those people there were completely and morbidly psychotic; but it was really interesting. I listened and kept my eyes wide open, never judged or got impatient with the pts, observed their tics, and listened to the nursing and medical staff and my psych nursing instructor re: what to look for and how to approach these patients. People HAVE gotten hurt at this state MH hospital; b/c there are so many acute and chronic, severely psychotic patients, but mostly b/c a staff members were not following protocol or weren't attentive or just a douches in dealing with people that are rather far gone and are incapable of reason. You have to learn what approaches to use with the particular patients, and you have to work with other members as a team. OTOH, at the private drug rehab/psych hospital, it was such a walk in the park in comparison. And it was definitely A LOT easier than the RN job in any medical or surgical ICU I have ever worked.
Here's my point to all of this: while you are doing a job like this, where you could use some of the psychology--through probably not a lot, b/c most pure psych programs don't give you a lot of application or clinical exposure unless you are in RN school, med school, or unless you are in certain psych grad programs, you could work and go to school. You just have to be teachable, and in many cases, the MHH or BHU will put you through the training if you have had some psych education. This is a peace of cake job to take while you are completing your prereqs. Again, you just have to be observant, non-judgmental, and open to good training.
It's through this job you could also get some relevant insight about why medicine--or at least share about your healthcare experiences--it's good learning about dealing with people. Sure you have volunteering for that as well. But what a lot people don't get is that unless you are going into an area where your interaction with patients and families will be virtually non-existent, some level of psych is always at play; b/c it's a part of dealing with marred humanity.
Good luck, and try to save money wherever you can; b/c MS is outrageous enough in cost.
Also, I have to agree again with RobF in that, it's better to take lower credit ft load than going over and risking your sGPA and your cGPA. In fact, it's better to go PT and have banging grades, especially if you are working, volunteering, shadowing, etc. These other things are also important parts to the ms application.
Plus, really, you should try to have as much of life as you can now; b/c once you are in MS and residency, that will be very, very hard to have. I mean maybe if you are a great student, your first two years of MS you can still have a life, but M3-4 and residency will consume most of our life/time. You may well resent the process more if you ignored having an outside life when you could have; b/c the whole process of becoming a physician is very long. Read the tons of MS and residents at SDN with posts that show that they are in big-time resentment mode; b/c they are exhausted and feel like MS/residency is sucking up every bit of their lives. Why extend that if you don't have to? Keep that frame of time as short as you need to so that you won't have undue resentment for your chosen career path. Why do all of this if you end up miserable? And God knows, no one will want to work, let alone live with you if you become a miserable person. Major downer.