Let me say this, even though getting into postgrad Med is hard, with hard work and persistence, you should be able to get into it. My sister and a bunch of her friends all did a Bsc. They weren't people who had photographic minds, or people who could pick up new content extremely quickly. They were just a bunch of really hardworking people, in that throughout their course, especially the final year, they could be seen studying at the library until closing time. (Even the guards knew their names....)
All 5 out of 5 of them got into postgrad med, although only 2 of them got it at Melb. Others got a place at usyd, or other unis. (Can't Remember) The friend that was offered a place at Usyd had a H2B average (which I believe should be achievable if work is put into it), but with a good GAMSAT and interview. (which they also practised heaps for).
When they started uni, a couple of them were in a similar scenario as you, doubtful of getting into postgrad Med. (One of them had a 85+ ENTER, and I remember that my sis flunked the UMAT with a really low percentile). However, after 3 years of hard work, their efforts were paid off.
So, just try and believe that postgrad Med is a possible course for you, and work really really hard towards this goal. With enough effort, you will see the results of it =)