As there is no specific degree that increases your chance of getting into medicine, other than some prerequisite subjects for some universities, then you should do this:
1. Assume you never get into medicine
(which honestly may be a reasonable assumption to make in terms of guiding future choices, because so far you have had at least five opportunities to get into medicine - on completion of school, psych years 1, 2, and 3, and last year - and you haven't - and this is said not knowing anything about your circumstances etc, just stating based on what you've just said)
2. Find a goal to work towards that is not getting into medicine (noting that you could get into it along the way. For the record, I think that working in healthcare is better for the resume than a medical science degree at least from my own perspective as an interviewer). If you could see yourself being a nurse, then doing something towards that qualification is reasonable
(2a. Reflect upon what might be realistic as a goal given your life stage and circumstances. Would you be giving up on other parts of your life to continue attempting for medicine and would it be worth it? If you got into medicine would you be able to continue training through pathways once you graduated)
3. Take the first step towards that goal in #2.
You have already done a whole degree and part of a second degree when you could have been working towards something in #2. Given that you are only doing medsci for the prerequisites, if there is nothing that you want to do that medsci would enable further than your psychology degree then it doesn't make sense to continue it to completion.
The rest is up to the goal you chose in #2. Note I haven't stated "career pathway" because there are a lot of things you could work towards that are not a career pathway that are worth the investment of time (an example of a non-career goal would be something like starting a family if your partner was in a financially stable/independent position).
If you wanted to gain exposure to hospital settings, then nursing is a great way to do it provided you are up to the unique set of challenges that nursing poses (and honestly, I think they work much harder than we do in a lot of the settings I have been in.)